Activation code - TV provider sign in - unable to check box to get code to show

When I try to watch CBS, NBC, ABC, etc. I'm asked to sign in with my TV provider (it's Verizon FIOS). The next screen gives the typical information: "Go to <app/tv//appletv> on a computer or mobile device ..." and there is a check box which says, "Activation code" which must be checked in order for the activation code to show. However - using the Apple TV remote (I have a 4K) there is nothing on the remote (or if I use my iPhone as a remote) which allows me to put a check box in the 'activation code' box so I can't get a code to activate the app.