I can't transfer songs purchased on iTunes to my iPhone

I did an update to IOS 6 on my iPhone. Thought I had backed up my photos and music. The music is there but not the photos. The music is in my library but I can't move it to my phone. I selected "authorize computer" and entered my Apple ID and password. When I clicked the Authorize button, I'm getting a message that indicates my computer is already authorized. When I purchased the songs from iTunes, I did it directly on my phone. What am I doing wrong?