How do you do a blowjob??

UPDATE:

Ok....so do to some rude people commenting on my post about not believing I was an adult and old enough to be doing a blow job, I will reword my post! 🤦‍♀️🤦‍♀️🤷‍♀️

Yes, I did grow up sheltered but now I’m an adult and I felt like this was a safe place where I could ask these types of questions. So....

Do you suck or blow during a blow job? And will it make me gag if he comes in my mouth? Please help me because my SO wants me to give him a blow job but I’m kinda nervous.