It depends what FT event you turn up to.
If you're talking about entering a local regional event like a Winter League shoot, then the rules vary from one region to the next and you're best off getting advice from the FT comp sec in your region.
So for example if you were shooting in NEFTA and you shot in say a NEFTA Winter league event, then you would have several options :
1. Shoot a PCP as an Ungraded shooter for 3 events until you get a grade
2. Shoot a PCP but in SFT Class (no big scopes, no dialling) - this isn't a graded category so you wouldn't get a grade.
3. Shoot in Open class - in this class you don't need to shoot the positional lanes (standers/kneelers) in the prescribed position, you can take all of the shots sitting. This isn't a graded category so you wouldn't get a grade.
4. Shoot Recoiling/Springer. You score percentage is worked out from the top PCP score of the day, but you are only competing against other springer shooters and it's not a graded category so you wouldn't be graded.
If you're talking about entering a BFTA Grand Prix - you don't have any option but to shoot ungraded as a 'Guest'.
Best bet is to let us know what club and competition you're thinking about taking part in and a representative from that region/club will be able to tell you exactly how the grading system works for that event.