A321 Navigation Radio

I'm having trouble working the radio in the A321. I can just autotune the communication radio, but I can't work the nav radio. In the 373 you can just click the actual numbers to change them, but it is not possible to do this in the A321. Only the tuner knob is clickable, and it only alters the numbers right of the decimal point.I'll be going to Denver in 2 days on an A319, but I'd rather not ask the pilots how to work the radios...