Host or join an Ideal Flight multiplayer flight:
From IF the host chooses the date, time, departure airport, and aircraft. Then the host decides on the destination, and generates a flight with the desired plan.
From IF, everyone else places themselves in the same airport, although they get the date and time when entering the hosted session, none the less, it would be better to enter the time and date the same as the host. Choose their aircraft, and generate the same flight as the host with the same flight generator settings.
Now everyone goes into the flight with the Fly! button. Once in the flight, end the flight and choose the Multiplayer screen. The host starts hosting the session and the others join in as usual. Once you all take off and land you can Alt+Tab to IF and end the flight for the score and records.
The host machine could run the Tower view instead of the Fly! button. If it is just for hosting, then no aircraft is introduced, and the airport can be viewed from the host machine tower view.
The only difference with the tower controller view is you have to "Load Flight" after going into "Host a Session", at the "choose session conditions" page. Press the "Load Flight" button and choose "ICAO Tower Controller View" from the list. ICAO would be your departure airport.