So I finally worked out how to join the Brotherhood of steel. SOO much walking.
Find Abby’s bunker in the North part of the Mire, there is a computer with a note on Fort Defiance in that bunker,
Find Fort Defiance, its the green building next to the Cranberry bog in the Bottom Right of the Map.
Head into the building (you don’t need to do the Event outside).
Find the reset switch for the locked door (Top floor on the right of the building after switching it the door will remain open.
Fight your way to the top of the left part of the building, there you will find a brotherhood area with a locked elevator.
It will tell you that you need a government ID to sign up, the way i did this is the quest at Camp McClintock to join the US Army.
Next head down to Charleston in the bottom left of the map above the Ash Heap, you need the government building specifically the DMV area.
To the Left of the entrance there will be a terminal that allows you to get a Government ID (1st Option)
Follow through the prompts on the quest (a few simple fetch quests) eventually you will get a Military ID.
Head back to Fort Defiance head back to the terminal at the top of the left path in the building and register for the Brotherhood of steel this will complete the quest and grant you access to the elevator as well as start some more quests.
Original Link – Continuation of discussion