A GM applies for
one simulation (map) at a time. To develop a simulation, go through the following steps:
1. Decide what you're going to playtest. Is it a class? If so, make a bunch of enemies and maybe a souped-up boss of that class.
2. Make your map. I recommend
the tiled map editor. Please consult the this thread if you have trouble making your map as it can be a little difficult if you've never done it before or lack a tileset. Also generate the enemies, NPCs, bosses and the like that the playtesters are going to face. (To do this, just make a standard character of a given class per the Player's Handbook and either roll for levels or raise 2-4 different stats of your choice for each level, and assign weapons/items. Remember that normal enemies usually do not get character/class skills, but bosses may).
3. Create some pre-set player characters for the playtesters OR ask them to make characters within some constraints.
4. Link to the version of the Player's Handbook you're using and any additional DLCs.
5. Post about it here for us to look over. If it looks good, I'll put your game in the queue and run it when the time comes!
I do not recommend newbie GMs attempt all this without guidance or previous experience. It can be overwhelming if you've never developed a FEF game before.
You may also request a veteran playtester (someone who has GMed and/or played a FEF game for some time) if you would like better input, much like the Mafia subforum