Credit Tips?

Hello, I am a 21 year old women going to college (funded by scholorship and parents), living on my own in an apartment with my S/O. I make around 1,200/month, she makes around 1,400/month. We have a budget we follow every month.

My main concern is I just got a car loan for 1,200 dollars with a 15% APR. We're paying it off in 12 months. That said my credit is only 617 and . I have no bad credit, or hard inquires or or collection accounts no late payments etc. The thing is I don't know how go build credit when it is so low. Is it a matter of waiting as I pay off the car or should I apply for a credit card and if so, which one?

Thanks! :)