How to add Junk Mail folder in mail app

I have a pop mail account with Time Warner that I added to the mail.app on my iPad. I noticed today that the mail.app on iPad does NOT show the Junk Mail folder. When I logged into my pop mail account on line, it showed I had over 100 junk emails and some of them I needed to see, yet the mail.app never pulled any of them off the server. How do I get the mail.app on my iPad to display the junk email folder?

Thanks