At vice admiral you have earned your maximum amount of skill points, you cannot further increase your skills.
If you don't like the way you distributed them, you can visit a skill trainer to respec. You should have earned free tokens while leveling up, if you have none left you can buy a respec token in the c-store.
just to add, that while you don't gain any skill points for your character after reaching VA, those points you "would have earned" from quests, seem to get added to the skill points for your boffs - e.g if a quest gave 1200 xp and 1200 bo xp then you would get 2400 points for your bo skill point pool.
As others have said unless you are a gold player (and have been getting the respect tokens as you level) then you will need to buy from the c-store (either deposit some real life cash or by converting dilithium on the exchange)