How do you get to the National Guard armory in fallout 3

I consider this building unaproachable until I find all five of the Keller Family Scripts holotapes. They give you the code to enter the room that houses the most sickening devastating weapon in the game... the Experimental MIRV. Basically, it's a Fat Man that spews 8 Mini Nukes at once, causing massive explosions.

Finding the tapes is a whole mission in itself because they are vastly spread across the Wasteland in various nondescript locations. Some out in the open in unmarked areas.

Once you find these tapes, simply go to a walkthrough site and read up on how to navigate the National Guard Building. Good luck.