Hi Paulette--
There are two ways you can do this:
1) If you have a custom version of custom/lib/editmenu.cf, you can modify the section labeled "EditPopup", and the changes will appear in all instances of the edit window context menu.
2) You can use the menu_add command in an ACL script file, with the menu called ":EditPopup", just as you would to modify a normal top-of-the-window menu.
Hope that helps.
--Clay