Occasionally you may come across a video file that comes with a separate subtitle file. In order to view it on your PC you just have to use a program like BsPlayer.
However, if you are going to play the video in a domestic player, you will have to embed the subtitles in the video file. This task can be very difficult to pull off if you don't have the right software.
With AVISubtitler, you just choose the video file, the subtitles, and the format in which you want them to appear. You then have to determine which codec you want to export the resulting file in.
The processing time varies, but depending on the final size, the process usually takes twice the length of the video (a clip of 30 minutes will take one hour to process).