Help ME! :(

Hello and i just started using blender to make a KSP mod, and whenever i deselect a object i can never edit it again, so i have to delete the object and re-add it. I have looked everywhere and could not find a way to get the edit menu back, so if anybody could tell me how that would be great!

You only have the option to change the parameters of the primitives objects when you add them to your scene.

Just go into edit mode (Tab key) and edit the mesh.