Read books with good romances, talk to people who have been in love, and go with your intuition. If your characters have never been in a romantic relationship before, that’s even better–they have the same amount of experience as you, so writing their perspective should be easier.
As everyone else has said, there are lots of different kinds of romances. Maybe pick one that’s easiest for you (like a guy and a girl becoming friends, then liking each other after that) and get comfortable with it.
Lastly, trial and error is always good. Play around with some different stuff. Get feedback from someone who is honest but encouraging.
"Beauty will save the world." - Dostoevsky