Phil
Going back about 10 years so the memories possibly hazy - however:
Open up the airports data file with a text editor (windows notepad or wordpad will do). Each airport will hava 4 digit Final Approach Fix level in the region of 1500-2500ft. You have to establish the aircraft at this level at the FAF for it to commence an approach and land. There is another key function which will get the aircraft to fly the approach but that info is all in the 'Help' tool in the utilities bar along the top.
CM