Deleting files from Sony Walkman NW-A35

Hello, I downloaded music files from iTunes to a new Sony walkman mp3 without the Content Transfer app (didn't realize I needed it). After I discovered my mistake, I am unable to delete the files and they have taken all of the storage on the device. I have tried to click on the folder button to delete it, but it does not respond. There are no music files on the device. thank you for your help!