After you have borrowed a DVD you need to unlock it before taking it home to watch. If you have already left, you will need to bring the DVD back in. You can unlock at any UAL library. 

The unlocking device is in different locations in each library but is usually wall mounted near the security barriers. 
Swipe the DVD through, and check to see that the little red padlock icon has changed to green. This will mean that the DVD is open