How to authorize on iphone?

  Hello,
My name is George and I was sent a link to an ebook from a professor. I was able to download it and get in on to digital editions without having to authorize it on my computer. When I was trying to get it on my cell phone digital editions app, it asks for me to authorize . Then it prompts me to create an account and then says to use my school account. However after this step it doesn't prompt to authorize anymore but just keep me on the adobe.com website within my UNCW account. I think if I can authorize the book I should be good but can't figure it out. Do you have any suggestions?
V/r,
George