Approach relationships with an open mind. Accept that you can and will make mistakes.
Treat your first relationship as a big learning experience. And then after that, have the attitude that you will carry on learning till the day you die.
There are books and youtubers you can watch that will cover the theory on how you should behave. But there's no substitute for actual first hand experience.
Plus if you have a good relationship with your parents then you should have some skills that you can transfer into your romantic relationship.