What you need:

New Kids on the Block t-shirt (choose one)

80s-style wig such as the following:
She-Mullet Wig
80s Style Madonna Wig
Blond Heavy Metal Rocker Wig
80s Glamour Girl Wig

80s fashion accessories of choice

Suggestion:
You can also dress up as a fan of other 80s bands!  Just pick out a t-shirt featuring your favorite!