EDLIN /? will get you the list of commands. Searching for the term will get you assorted references to its use.
It's a sort of VI thing... heh. It's a rudimentary text edittor intended to use with DEBUG to produce minimal assembly code and compiled programs. For an easier tool, try ELVIS (VI for the PC), it's more useful. For best results, get a decent text edittor (like Notepad or E88) that doesn't rely on arcane commands to just edit text... or is at least self-documenting.