Authentication

I am looking into integrating a forum into my web site.  Since my website already has a user subsytem, I plan to authenticate to my database which will have the required info replicated to the WWF DB. I've got that part figured out. 

My question is on login, it looks as if I need to set the value of the UID cookie, but have not been able to definitively determine if the value should be set to the usercode in the WWF DB, or some other value( author_code??? ). I have been searching the forum and the code for several hours.  Could someone elaborate on on the required cookie settings for UID and if other cookie settings are required?

By the way, great job on the forum software. 

The usercodes I have looked at seem to be encoded, like account name and then some numbers, is this just to make them unique?  or is the information in the usercode disected and then the extracted data used for other means in the forum?  

I guess the bottom line, can I insert my own usercode as long as I keep it unique within the column.

thanks in advance.......