editing a file to allow database integration

I bought both vbulletin and ProSupport which comes with a userlogin.class file which can be edited to call and use the vbulletin user database. Therefore making a clients login universal and working with multiple systems.

However, I havent a clue what I actually need to edit, I dont want to paste the code here as its 272 lines long. Therefore it is accessible at

http://l3d-design.net/misc/UserLogin.class

for viewing.

Any help on this will be greatly appreciated.