W5300n

I purchased a W5300n a few months ago and in general I love the unit. Last week I bought a 500-sheet paper tray to sit under the main paper tray. I noticed today that Tray 1 was out of paper but the printer did not pull from Tray 2. I went in the control panel of the printer and found that I could only set the paper size as "universal" and not actually "Letter". Any suggestions as to how I might get the printer to use Tray 2 when Tray 1 is out?

cF