how do I be a good Christian?

ca
Hey guys, so I grew up in a Christian household, but during highschool I got in the wrong crowd and turned my back on God with my personal choices. Now I'm in my early 20s, I'm engaged to a very loving but non believing man. And I'm trying to get through college. I don't know how to be a Christian again I suppose, I know the basics like confessing that I have sinned and believing that Jesus died for my sins... But there are no churches with people my age around me, and I don't know how to start hanging around the "right crowd" I suppose. Also, my fiancé is probably going to react very badly to wanting to wait until marriage before having sex again. I don't know how to switc. My life around or what to do anymore. I don't have any Christian friends either. Does anyone have any advice for me?