I've seen a number of posts and after calling the Ticket office and Ticketmaster, I figured it out. 

The tickets you bought throuh BYU were sent to Ticketmaster, using the same email as your BYU Tickets account. BUT, you access them via a special Alamo Bowl Portal.  So, go to this link:

Login using your ticketmaster.com email (must be the same one as your BYU Tickets email). 

If your ticketmaster email is different than your BYU Tickets email, you may have to create a new Ticketmaster account using your BYU Tickets email.

Apparently this was sent out in an email but I, and many others I've seen, did not get it (and no, it wan't in my spam either).

One last thing, BYU said they will have a person on-site outside the Alamodome to help folks who are having a hard time accessing their tickets.