This is the Brotherhood entrance section of the map of the wasteland presented by:
This is the main entrance. You can't get in without joining(sucks eh?). To join you have to talk to Cabbot, then for a little extra info the guy next to him. They will tell you you have to go to the Glow (the ancient order) to bring back a holo-disk found on a dead power armored body. To do this you must take 2 Rad-Xs before entering the area of the Glow and one after you are done. To get in you must have a rope to sling on the metal beam on the edge of the crater. Retrieve the holo-disk and get out, go back to the Brotherhood and get in. Spend some time learning and other stuff then come back to the glow and do what it say in the Glow part of the walk through.