Bottle feeding

My son is 6 weeks old and today I pumped for the first time and tried to bottle feed him. He just seemed so confused by the bottle and wouldn't suck at all. I don't actually need him to take a bottle until January which is the first time I will leave him (for around 6 hours) but I just want to make sure he is comfortable feeding from the bottle by then. I am using a Medela pump and bottle that my friend gave me. Any tricks?