You cannot change these settings. Two thick vertical bars will appear on the editor screen representing your margins as they are currently set. Set your margins from here. As you press these keys, the vertical bars will move one space at a time. All function key assignments are displayed at the bottom of the Editor screen.
Assignments are different for each sub-menu.
The tables in the following sections list the function key assignments for the Editor main menu and each of the Editor's sub-menus.