(Since so little actually happens in this play, here's the very short list of things Jamie actually does. If you want a timeline of how his character develops through conversation, which is more important to a play like this, head to the "Detailed Summary.")
Jamie laughs with Edmund in the dining room before finally entering the living room and talking with the family.
He goes out to do yard-work with James.
He re-enters the living room a bit before James, and nabs a glass of whiskey with Edmund.
They both speak with Mary until James returns for lunch.
Jamie stays in the living room talking until it's time to change for lunch, after which he goes into town with Edmund and their father.
He spends all afternoon and evening drinking and hitting up the local brothel.
He comes home well after midnight, drunk, and stays in the living room with James and Edmund until Mary's climactic "mad scene" and the end of the play.