Did you try reading the tutorials in the Editors Depot? Plenty of tutorials there explain how to do these things.
In any event, the
exact location for your briefing depends on your OFP installation. The default directory would be the following structure:
c:\windows\program files\operation flashpoint\users\
YourUserName\missions\
YourMissionNameIf it's not obvious enough, replace
YourUserName with whatever your user name is in the game, and
YourMissionName with the name of your mission.
As I said, this would be the
default structure, but if you didn't use the default, this would not be true on your computer.
As for "access[ing] the gear," could you be more specific? Do you mean as in being able to choose weapons during the briefing phase? If so, browse the tutorials related to the
description.ext file. For example, try the one by pcverden:
http://www.ofpec.com/editors/tutorial_view.php?id=18