I'm going to yell at my step dads friend
Why do you want to yell at your step dad's friend?
If he wants to go inside my house he needs to knock, not just walk in!
Walking into someone's house without having been invited is rude. You should tell your step dad's friend that, but try and not yell as it may escalate things unnecessarily.
I'm going to tell him to go fuck himself.
cursing or any kind of yelling will only make you look bad. Your stepfather would punish you if he finds out you talked to his friend like that.