Now Unreal was a game I made many levels for, much more than are listed on the side. The Unreal Editor did away with so many of the limitations of making Quake 2 levels, and so I was free to make almost whatever I wanted. The maps that are not listed here were either learning maps which weren't that great, or unfortunately got swallowed up by the boogieman that lives in my hard drive. In the end, the only maps remaining are all remakes of various Looking Glass Studios games.
To install an Unreal level, simply unzip it into the unreal directory and the files should go in the right spaces. The Pits of carnage maps have no extra components, so just unzip them into the maps directory. The maps should appear in the list when you go to start a multiplayer game/botmatch.
If you want to make your own maps, use UnrealED! If it's not on, you may need to install it from the Unreal CD.