Hi, Oceanlove101.
So, the deal with readiness is that there is no age or point in your life or relationship when you "should" be ready to have sex, and being ready for sex isn't something that tends to happen once and then you're always prepared. Someone might feel ready with one partner, then start dating someone else and not feel ready to have sex with them. Long story short, there's nothing wrong with you for not feeling like sex is something you're ready for, now or ever. Pretty much the same thing goes for knowing what to do; that's something we learn over time, and it's not universal because every person is different, with different likes and dislikes, so figuring out what you enjoy and what your partner enjoys is a learning process, not something you can just know.
I also want to check in with you about what kind of sex, specifically, you're referring to here. Many people mean penis-in-vagina intercourse when they say sex, but that's just one kind of sex, and most people would probably find it a bit confronting to jump straight to intercourse when they've never had any kind of sex before. So, if you've never been sexual with your boyfriend in any way before and you're concerned about having intercourse, that's jumping the gun a little bit: if there are some kinds of sex you feel ready to try, like manual or oral sex, then you can start there and see how that goes and whether or not you're comfortable with it, and then add intercourse into the mix if you want if and when you feel ready. (And obviously, if you aren't ready for any kind of sex right now, that's totally okay too.)
Per your concerns about pain, when it comes to vaginal entry (with a penis, fingers, or a toy), the most common cause of pain is a lack of arousal and a lack of lubrication. And not being aroused enough, or not having enough lube, can make things painful whether it's the first time someone's having sex or the 100th time. If you are ever in a situation where sex is painful, that's a cue to slow down and go back to things that feel good for a while, add a bit more lube if necessary, and try again when you're feeling a bit more relaxed.
We have a few different articles on the main site that I think might help lessen some of your worry around this:
What's Sex?
Yield for Pleasure
My Corona: The Anatomy Formerly Known as the Hymen & the Myths That Surround It
I'm wondering too if becoming a bit more familiar and comfortable with your own body and anatomy might help alleviate some of your worries as well. You don't have to masturbate if you're not interested in doing so, but taking some time (and a mirror!) to get familiar with your genitals may help you get a bit more comfortable with the idea of someone else touching them. This piece is a great place to start with that:
Innies & Outies: The Vagina, Clitoris, Uterus and More