You cannot control the UHF radio through the UHF panel on the left console unless the CNI knob on the AUX COMM panel is set to Back Up. When this knob is set to UFC as it normally is, the radios are controlled through the UFC (Up Front Controls)—the ICP (Integrated Control Panel, under the HUD) and the DED (Data Entry Display) to the right of it. Watch what the DED says; that is what your radios are tuned to. The DED may say, for example, "UHF 297.50" and "VHF 13". This means your UHF radio is tuned to 297.50 Mhz, and your VHF radio to pre-set channel 13.

Push the COM buttons on the ICP (Integrated Control Panel, below the HUD). This will allow you to switch to either a specific frequency or a preset channel. To tune to Kunsan tower, for example, push 29230 on the ICP and then the ENTR key. To tune to channel 12, whatever frequency that may be on either the UHF or VHF radio, push 12 and then ENTR.

I hope this is clear to you now, but I'll gladly answer more questions if you have them.

Also, I should point out that the channel knob on the UHF panel is bugged in BMS 4.32. When you switch the CNI knob from Back-Up to UFC, that channel knob will stop functioning no matter what setting on the CNI knob. Needless to say, the BMS devs are aware of this issue.

EDIT: After re-reading your first post, I see you're already working through the UFC. The above is still valid, though. Push the COM1 button, enter 15 on the ICP, hit ENTR and there you go, you're tuned to Uniform 15.