Well, I'm still confused, but I'll try again: please forgive me if you already know this...
1) Make Editable will turn a 'primitive' object (a cone, cube, sphere etc) into a generic polygon object. Primitives can be edited parametrically (eg change the radius of your sphere, or change the number of sides on a disc), but you can't edit the individual points or faces until you convert a primitive into a polygon object.
2) Once you've converted your object, you can select either points, edges or faces with the selection tool to edit them, but you must first be in either point mode, edge mode, or face mode (use the icons at the top of the main C3D window). While making your selection, you can use the Selection menu to help you (eg Select None, etc).
3) Once you've selected the bits you want to edit, you may want to use the Transform tool to move them around using the gizmo.
Does this help answer your question?