How to become a naval officer?

So right now Im currently Enlisted in the Navy, Im a Nav ET on submarines I've been weighing my options about staying in or getting out I'm interested in applying for STA_21 but i know i don't quite have all the credentials i know i gotta take the SAT this fall, and i may or may not have enough college credits i spent a long time in training to become a Nav ET and i took a class before the navy, so can i use a lot of those credits towards my package? i know you would need enough done to finish a degree in 3 years. So i know i need to work on these things what else are they going to look at if i decide to apply, their going to look at my evals of course right? what can i do to improve my chances the best? Is it harder depending on what you want to be, i want to be aviation. May take me a while to get these credentials but i know i can do it and im just barely 20 so what if i got out did 2 yrs of college in the navy transfered to a university finished and then applied for OCS can i do that? Which is easier to do? thx for the feedback if your going to leave some im still unsure about this but i want to act like Im going for it so i have the resume for it just in case, it sounds really good.