Zoom in until you can see the FIR boundary(Green lines), the press and hold on the green boundary for a few seconds and release. Press on the desired area you want (it should make that area pink) and display the info for that FIR area. There is also an additional Communication tab for frequencies. As far as I'm aware, this is the only way to get the frequencies. I don't think you can have them displayed on the map.
This info can be found in the settings> help>overview