The tools you need to edit ArmA… are the following:

For Texturer: GIMP / Photoshop, Texview2 / Pal2Pace.

For Modeler: Oxygen 2.

For Map editor: Visitor 3 / WrpTool and Wilbur.

For Config writer: Notepad++ / EditPadPro.

For Mission maker: nothing (perhaps Notepad++ / EditPadPro for scripts).

That's the required tools in a nutshell. We can then dive more deeper into the finer details of what tools to use (for example who likes free Gimp over commercial Photoshop etc, how to use WrpTool with Visitor 3 etc), but that's the quick summary for newbie ArmA editors. Also there is small tools like cpbo, binpbo etc but those are sort of included in the BIS Tools package. These are the generic tool names you need to know to get around in ArmA editing.

Tools NOT to use: notepad, wordpad, MS paint. Just don't do it :)