Hello my alt charactor is a fed sci officer.( not bridge officer) I have read somewhere on the forum that my fed sci officer can use my fed tac officer ship without buying one.Or is this a fleet thing or something else?
Sorry. You can't trade ships between characters... unless they are some type of reward ship that comes in a box and you haven't opened it yet.
Where you may be getting confused is that C-Store ships unlock for the whole account. Therefore, if your Tac officer bought, say a VA ship for instance, then your science officer would also be able to "claim" that ship for themselves at VA.