You bid for domiciles while in training, and when a vacancy bulletin comes out (depends on time of the month you start), the awards include those in training. There are no guarantees of LGA being available when you're in the mix, it all depends on who leaves what bases and where everyone else wants to go. The overwhelming odds are that LGA will have openings, though, historically not too many people want it. If it doesn't have vacancies, the next time a vacancy bulletin comes out with openings in LGA, you can probably get it unless some folks senior to you want it. Your bid is a permanent bid that stays on file for all vacancies until you change it with different desires, say you want CHO after a year.