How can I see ACC, TMA, etc frecuencies?

When I use VATSIM i would to know prior the transfer of the ATC which is the frecuency that I have to use to have it in STBY l, but in the charts didn’t see the frecuency of a ACC or TMA, even in the map where appears the limits of the ACC’s.

Where I can find this frecuencies in the Navigraph app?

Thank you in advance :slight_smile: