How to use the Burn app on Mac os x to burn dvd?

You didn't mention which computer you have. Is it Apple? Did it come with a DVD burner? Apple provided iMovie and iDVD which is EVERYTHING you need EXCEPT the codecs for the outdated AVI format. Get that by downloading Perian, link below. Perian will enable your Apple programs to use AVI and FLV (Youtube) files. You don't have to download any of those other things. That is not to say those other apllications won't work. They may do the job as well, but why spend time learning some off-the-wall applications to duplicate the abilities you have in iMovie and iDVD?

Step 1: Download and install Perian. It simply provides the conversion software that works in the background. You don't ever need to do anything with it.

Step 2: Open iMovie, choose"New Project", and choose where to save the project. {a project has the movie file, plus any special effects files you add from iMovie that can be merged into the final DVD movie}. Go to File > Import. After you import the AVI file, move the thumbnail(s) to the bottom of the iMovie window to arrange them in the Clip Viewer. Add transitions or titles if you need them by following the iMovie Help.

Step 3: When done, click the iDVD button at the right to add chapter markers, if you need them.

Step 4: When done, click the "Create iDVD Project" button to launch iDVD. Use iDVD Help to learn how to add a menu and chapters.

Step 5: When done, click the burn button. You will get a message to insert a blank DVD. Use Verbatim brand if you have any trouble with other brands (big name is no guarantee when it comes to DVD quality).

If the iDVD can't burn your videos to dvd on mac, you can try another Mac DVD Creator from Wondershare.