how do I have an orgasm

Okay so for starters, I've never had an orgasm before. Until I met my boyfriend, I wasn't really into sex type stuff at all. I hadn't really ever masturbated, certainly hadn't had an orgasm. Also before I met my boyfriend, I went on antidepressants. Now, I really wish I could have an orgasm when I'm with my boyfriend. I'm still not really interested in masturbating, I sort of only get aroused when he's around. But I'm not sure how to have an orgasm because it's probable the antidepressants are making it hard for me to have one, and the fact that I don't know how to have one in the first place is making it difficult too. I just really don't know what to do so any advice would be great