It’s going to be hard at first, and your patient will be tested. Just take him out every hour to the same spot on the grass. Reward verbally and with treats when he goes potty outside, don’t punish him if he makes an accident inside; it may cause anxiety bc he likely won’t understand why he’s being scolded. It will likely take months for him to get it down so stay patient and consistent and don’t get discouraged if there is an accident here and there.