Do I have to do the opening game tutorial before I can enter that key? I want to mod this game but nexus said I didn't have a fallout ini file or something. and the dlcs weren't showing up in the mod manager either. THis his highly annoying as I grabbed all my mods and that, and now the game keeps crashing in the beginning, even with all the mods turned off. I just want this damn thing installed properly. Sorry, but this is frustrating, I have wasted 3 hours now with downloading.

Run the launcher, start a new game and just let it run for a few seconds. Then close the game. You'll have the full INI file required.

Ok, thanks. I'll try that. When do I have to put in the key from steam? it keeps saying that I need to put in the key when the game asks for it. But it never did during the tutorial part of the game.

It should have asked it before it started installing. If you bought it from steam you don't need the key at all.

Oh, wait this is the Fallout 3 section Only way to get it with steam is to buy it from steam (unless that has changed), so you don't need to worry about the key.