This trill is in my music and I don't know how to play it.
fff so obviously very loudly. Note that probably the whole trill shall be very loud; a loud sharp attack would be better noted sfz, but actually, both interpretations are possible.
Then it's easy: you play the thrill on F-G the whole time. Accidentals don't have to be repeated after a tie, so there is certainly no F# involved.
The final eight-note G staccato just tells you that you shall end in G and that the G shall be prominent; not necessarily very loud, but the audience have to be sure that you intended to end in G rather than F (or fade out or whatever.