Fist thing you need to do is bump into your club secretary, but, to get you started.
FT is shot in a sort of two tier system; regional and National.
If you are a member of a club in the region, then you can enter a regional competition, usually by turning up on the day but you need to check on the specifics.
To enter a GP you need your club secretary to apply for a BFTA card for you. Once you have one then entry to GP's can be made on line via the BFTA web site.
Regionally you will start in C grade and as you scores improve over time, so will your grade. Nationally you will start as an ungraded A grade, and after three GP's you will be given your proper grade by Simon Evans (gradings officer).
I'm glad your enjoying shooting FT, it is an extremely enjoyable / frustrating / fascinating shooting discipline.
Hope to see you at a GP sometime.
"I'm your huckleberry, that's just my game"