1. Open Source SDK
2. Press Add Game Configuration
3. Browse the Directory
4. Goto C:\Program Files\Steam\steamapps\sourcemods\*enter sourcemod here*
5. Now press select then add it.
6. Restart Source SDK
7. Open hammer
8. Goto the Tools tab then click options
9. Delete the thing that says base.fdg at the end then click add
10. Go into your sourcemod folder and find bg2.fdg (or w/e your sourcemod is) then click add
11. Your done!
You forgot before step two to press 'Edit Game Configuration' then to click on add ;)
i can't find the bg2.fdg