Cannot sync music to my iPad!

I have downloaded the new iTunes so far, but I can't sync music now.

First I plug my iPad, then I click "iPad" and it shows the summary. Then I see what's on my iPad and I click "Add to.."

So I see the albums again and I drag them to my iPad.

I mean I watched the new iTunes video and saw how to do it, there isn't any problem until there.

When I drag the songs, what happened in the video doesn't happen! nothing happens!

This is annoying. Please if you can, help me