Q: why i cannot search any music on my itunes? is it necessary to register and pay an annual fee in order to usa the itunes in your ipad?

To search your music library on your iPad, use the music icon.  The I tunes button takes you to the store where you can buy more music or videos.     To play your won music etc you do not need to be connected to apple, the music is on your pad.

If you want to get new stuff from iTunes, and load it onto your pad, you need an account.  Your account is your apple id.

iTune Store is not available in certain countries. Check here:

http://support.apple.com/kb/TS3599