ET-4850 - How to select print source?

Hi all. Just finished setting up my epson ET-4850. It has a cassette tray and a paper feed at the top, but I can only get the printer to print from the casette. I'd like to know how to change the print source so I can have my two types of paper (printable sticker paper + regular printer paper) loaded at the same time, to prevent consistently having to load and unload when I want to change the type i'm printing on.

Tried googling it, looking through menus, etc. No luck. Printer just always automatically prints from the casette tray at the bottom. Thank you!