TLDR warning!
Object/armature orientation
If you add suzanne to the scene you will notice that its orientation is different, this is because your character is facing the wrong way.
To fix this, first select your mesh and Apply Object Transforms (rotation). Then change the mirror axis from Y to X in the mirror modifier. In edit mode, rotate 90 degrees along the z axis (with merge and clipping disabled), then reenable merge and clipping and move the mesh along the x axis until it merges together.
Next the armature, in object mode set the x transform to 0, then rotate the armature 90 degrees in the z axis so it lines up with the mesh. Also, it’s probably better if the character is not below the grid, so move the armature above the grid (along the z axis). Then apply object transforms (rotation and location).
Next the mesh again, in object mode move it up to match the armature (up and forward) then apply object transforms again.
Armature bones (edit bone)
You’ll have to name the bones. The bones on the left side of the screen should have a .r suffix, because they are the bones to the right from the character’s perspective. I’ll use _r and _l because I’m used to unreal engine 4. For the legs, Bone.001 to upleg_r, Bone.002 to lowleg_r, Cpied.L to ik_foot_r (or Cpied.R if you want), Bone.004 to foot_r. Then name the other side the same way but _l. Repeat this for the arms (your bones that say .L should be .R or _r or whatever).
When you have fixed the bone names, enable X-Axis Mirror in the Options tab to the left of the screen, then select all of the bones to the right of the middle of the screen (to the right of the head/spine bones etc), press the translate key (grab command) and press enter. Then your bones will be mirrored correctly.
Then, select the bones that are either IK bones or pole targets (C1bras.R, C1pied.R, Cpied.R/ik_foot_r, ik_hand_r and the mirrored bones) one by one and ensure that Deform is disabled in the bone panel.
Armature (pose mode)
For now just select all bones and clear transforms. (alt+r, alt+g etc)
Mesh (object mode)
Delete all vertex groups by clicking the black arrow in the Vertex Groups panel (under object data, vertex triangle icon) and choosing delete all groups.
Parent the mesh to the armature with automatic weights. Your mesh will look really twisted and strange but it’s fine for now.
Armature (edit mode)
Enable X-Axis Mirror (if it wasn’t). Now move the pole targets for the knees so they are actually in front of the legs. For the legs, select the tip of the bone between the upper and lower leg and move it slightly forward so they are bent forwards.
For the elbow, move the tip up and slighty back so there’s a slight curve. For the elbow pole targets, move them behind the arm itself. Also move the knee pole targets further away from the body.
Next, select all of the bones and do Recalculate Roll (search with spacebar) and choose global Z axis. Then, for every bone, set the roll to 0 degrees.
Armature (pose mode)
To fix the twisting, go to the IK constraints and change the pole angles. For me, -90 degrees worked for the legs, 0 and -180 for the arms.
Mesh (object+edit mode)
So I forgot to fix this, but since you made your model with a weird mirror, the wrong side is mirrored. To fix this, in object mode, apply the mirror modifier.
Then change to edit mode, select the middle edge loop by shift alt selecting a bunch of times on the loop right in the middle. Do Rip and press enter. Next select the part to the left of the screen by pressing L (Select Linked) and delete the vertices.
In object mode, add the mirror modifier again and put it at the top of the stack. Finally, there seems to be some strange mirroring going on with the vertex groups, I don’t really know why, but you can fix it by selecting all vertices, then clicking Remove in the vertex groups panel for each bone ending with .R/_r. You can also select the vertices for the legs/arms and do Remove for the middle bones (Ventre, Torse, Tete).
Armature (edit mode)
So now you probably want a hand bone, extrude one from the upper arm bone along the x axis.
Mesh (object+edit mode)
Make two new vertex groups and call them hand_l and hand_r (or whatever you named the bones). Then go to edit mode, select the hand vertices and do Remove from all groups in Vertex Groups. Then Assign them to the hand_l bone.
Armature (edit mode)
Now you need to parent the bones. Actually make a new bone first and call it root by doing Snap Cursor to Center and add a bone there and naming it root. Next, select all of the pole targets and IK targets and finally the hip bone, then parent them to the root bone with ctrl+p, keep offset.
Next, the legs, parent the upper legs to the hips with the same method. Finally parent the foot bones to the lower leg bones (with connected) and the arm bones to the torso (with keep offset).
Now the rig kind of works but you can do some things to clean it up. For the leg bones, make sure they are straight in the front view. Also you can make them a bit longer (upper leg and lower leg bones).
Oh right, I remembered why the vertex mirroring was strange, your mesh had incorrect normals, so select all vertices and do Recalculate Normals, then you can do automatic weights again and get really nice weights. You can make the upper arm bones a bit longer to make them act as a pseudo clavicle bone (and get nicer deformations). You can also enable Preserve Volume in the armature modifier to make deformations look better.
Object mode
The final thing you can do is to make some nice looking widgets for the IK targets. Make a cube in the center, call it wgt-cube or something and move it to a different layer.
Armature (pose mode)
You can select the IK foot target and go to the bone settings, then Custom Shape: under display, choose wgt-cube and enable wireframe. It will be pretty huge, so you can scale the cube mesh itself down (in edit mode) to make it look smaller. Do the same thing for the other IK foot target.
For the arms you can do the same thing or make a new mesh for them, usually you make a mesh that looks like a hand. Also you’ll notice that the IK hand targets are too far away from the body, you can go into edit mode, select the hand bone, do Cursor to Selected, select the IK hand target and do Selected to Cursor and it will snap to where it should be.
Then in edit mode for the mesh, select all vertices and do Faces: Smooth in Shading/UVs to the left. For the faces with wrong materials you can select those faces and in the material select screen pick a different material and click Assign.
That is pretty much it, maybe I forgot some stuff, this turned out a little bit disjointed, but you can say if you get stuck anywhere. You should try to recreate this yourself now to learn the techniques.