I've read the manual of AGS and it says i could add music to my game, but i can't found the section
where it is?
Music and Sound (http://www.adventuregamestudio.co.uk/manual/MusAndSound.htm), and the Multimedia functions (http://www.adventuregamestudio.co.uk/manual/Multimedia%20functions.htm) will probably help too.
Try using the 'search' function - both on the forums, and in the manual itself.