How do you teach your puppy that outside is for potty?

I’m at my wits end. He dos t even seem to understand that outside is for potty. I’ll take him in the morning before he goes inside and stay out there for half an hour and he whines like he has to go and tries to go inside. Once i reach my limit of keeping him from using the potty we go inside and he finds his box to go potty. He’s 5 months old, totally litter box trained from the person we got him from and doesn’t even get that outside is for potty. I don’t know what to do anymore.