When you click on Add the following window opens:
Let say you want to add the Phoenix Deer Valley Airport. You can enter "KZ-KDVT" and press
enter or if you don't now the ICAO code you can check "Search in all field" and put part of the
name. If you write "deer" and press the "Find" button, all the waypoints with "deer" in the name are
listed. Then you click on Deer Valley. If you want to use the keyboard hit the "down arrow" until
your airport is selected and then press Enter.