ILS frequencies can be found on the world map. You need to enable NAVAIDS in the filters. For a particular runway, the ILS name and frequency will be under the navaid icon at the opposite end of the runway.
Example: IBUL ILS RWY 9 at KMIA frequncy 110.90
Even if you have Jeppesen charts It’s a good idea to check accuracy on MFS’s charts just in case the ILS is missing or the frequency is wrong.