I don't know what you mean by "first place". To get the handles in and out of a point between two straight paths, you use the Convert Anchor Point tool and drag. You WILL get both sides (if path runs each side of point), but they WILL be 180° to your drag (straight line). Now if you wish to just move one handle without the other moving, this is where you use the Direct Selection tool with the ALT key held down. Only the handle you grab will move to your swing and drag. If you hold down ALT key when using the Convert Anchor Point tool you'll duplicate the original path while creating the bezier handles at that point.