All info should be here:
http://www.brca.org/?q=content/110th-electric-road/127
I would recommend looking at entering your local BRCA 2012 Regional championship before considering entering National events.
The places at Nationals are highly desirable due to number limits and it is down to your BRCA 'F' (formula) skill grading whether you will get entry as entry is prioritised to higher F graded drivers.
As a Beginner you will be F5 and the pro's are F1 graded, everyone else races to be inbetween and attend regionals to gain these F gradings, which are awarded on championship finishing position.