camping
The Forestry Service operates 32 campgrounds within the forest itself, which bear nominal fees during the summer months. Potable water and toilets are available at each site, while RV hookups most often are not.
lodging
Custer is pretty much the "hub" for the forest, if you can call it that, and is the best place to find lodging.
backcountry
As with most any U.S. National Forest, you are free to pitch a tent pretty much wherever you like, provided you are at least 50 feet away from roads, streams, or trails; that you do not take any road marked private; and stay no longer than fourteen days they don't want people moving in.