you need to really follow the concepts they teach you.
The assignment should state what you need to do, always look back to the assignment sheet.
Ok so lets begin with the 4 main concepts of Pop culture:
It has to be related to a consumerist product - Consumerism
How is it accessed and to what limit - Access
The growth of the product from Local - National - Global - Growth
How has the product evolved - Evoloution of product
Ok so if you were to focus on The Beatles, you wouldnt be talking about 'The Beatles' but instead would be focusing on 'The beatles - the product', like the tangible product of The Beatles....confusing I know.
It would probably be easier to focus on Harry Potter because the whole thing is a tangible product and a culture has evolved from it.
Consumerism - The book, the movies, the toys etc
Access - easily accessable, just go to a bookstore, library, school library, cinema, television, Dvd's
Growth -(This could be tricky) Local would be where the book was initially released, National would be when it was a major book in britian and Global would be when it became a worldwide phenomenon
Evoloution - The books and movies become darker and more mature as time goes on
thats pretty much all I can do unless I know everything about the assignment.
good luck.