Wooh! Part three is probably the most annoying, if only because you get only one item for watching an episode of The Hills.
So, make sure you're next to Julie. If you exited out, don't worry-- just go back to it. Go up right from Julie until you see the theater. There's a small arrow at the top most part. Click that. When the options come up, click "To cinema".
You'll be transported to Julie's Profile.
FIRST AND FOREMOST, talk to Julie. If you don't, it won't register that you're doing the quest and you'll have to sit through the episode again to get the sweater.
After you accept the quest, you'll be back in Julie's profile. Scroll down and pick a theater.
Now, for those who are not fans of the show, you're probably whining right now about having to watch the episode to get the shirt. However, the episode loads extremely quickly, so you can click the time marker and drag it to the end. I wouldn't drag it all the way to the end, but to the last few seconds of the credits.
When it's over, click "Goto Profile". Time to Talk to Julie again!