Having trouble with the Kobo iPhone app?

I just added the Kobo Books app to my iPhone. I read a preview of The Book Thief and then bought it on their website: however, the iPhone would not download the file. I then went to the website on my desktop computer and downloaded Adobe Digital Editions as instructed, then downloaded The Book Thief there. My iPhone is plugged into the computer, but I now have no idea how to transfer the file from Adobe Digital Editions to my phone, since ADE makes no indication that it recognizes the device. I emailed the Kobo "24 Hour Helpline" but have not received a response yet. Has anyone else encountered this problem before, and do you have a solution? I would just get rid of the app, except that I paid 7 dollars for the book and would like to get it onto my phone if at all possible.