Monica: Listen up. There is usually only one dress in each size so when they open those doors, fan out. Now, this is what you’re looking for! Memorize it!

Explanation:

fan out   phrasal verb
if a group of people fan out, they walk forwards while spreading over a wide area

listen up   phrasal verb   spoken   especially American English
used to get people’s attention so they can hear what you are going to say:
Hey everybody, listen up!