How do I use the F-key buttons for comms?

[ElCuco68]

I've been wanting to fly the CASE III recovery mission in the F/A-18, but when I use the backslash button, after I hit F5 for ATC, all of the selections in the next menu are darkened out and can't be used. I'm reading the manual and will eventually learn how to use the radio the "right" way, but in the meanwhile, I wanted to be able to learn other procedures like CV landings.  Thank you!

[MadMonty]

Do you have easy comms on? If not, you will have to switch your radio (e.g. Comm1) to the correct frequency of the carrier and also have to press Right-Alt-backslash for Comm1.