If you don't have a license already then AB allows you to add 3 units to a list - you can use this to test that it will all work correctly, as it allows use of the autoupdater initially to download files. If you have an old license that hasn't been renewed, and you're using AB 3.2d or higher (ideally you want to be on 3.3 or higher, but 3.2d should work - not 3.2a, b or c, must be at least d!), then go to the Downloads > Supplemental Downloads link on the Army Builder website ...
http://www.wolflair.com/rightframe.php?context=army_builder&page=supplemental_downloads . Download the Warhammer 40k file, import into Army Builder, and off you go