I can see how to bisect but not how to remove the part I want to


This is as far as I can get! How do I remove the part I don’t want?

Also how do I divide a cube until it becomes a sphere? The tutorials on You Tube move too fast to see what they’re doing. Cheers.

If you mean using the bisect tool, look in the toolshelf for additional options or press F6 to show these in a floating panel


Also how do I divide a cube until it becomes a sphere?

Various options. Select all faces and W / subdivide, set the number of subdivisions you want. To make this into a sphere you could use a Cast modifier set to Sphere with a factor set to 1 or use the To Sphere tool (select all faces and use Sift+Alt+S, then press 1)