Extra Virgin... Help

I've never sucked a dick, and I've never actually had sex either. But the guy I wanna give my virginity to has expressed wanting to have sex with me (I don't call him my boyfriend BC we are in a on-off relationship rn)
Anyway, He likes to "pleasure" me in different ways when we make out... I would want to be able to suck his dick if he ate me out, ya know? Anyway. I just don't know. How it works. How it would feel to me. How will I know if I'm any good or not???