Need help with subtitles

hi all

I need some help with subtitles. I have a AVI file i want to convert to DVD format the problem is the subtitles are a seperate file .ssa , when i play the file in powerdvd 6 the subtitles work right, i want to change the movie to dvd using winavi but how do i get the subtitles to work when it is converted?I want to beable to put the disc in my dvd player press play the movie plays with the subtitles there allready.