When I launched the game, it automatically set the graphics at Medium. It runs just fine, but is a little choppy, so I'd like to set the graphics to Low for the time being so I can play before fine-tuning it later on. Does anyone know how to do this? I can't find an option anywhere to set the graphics to Low.

If it's like FO3 try the launcher.

Yes exit and restart the game. From the main launch panel select options and from there you can adjust the graphics settings.

Thanks. Tweaked a few settings, and now it runs beautifully.