There is no easy way. I found a freeware program that would let you author a DVD based on avi files, but I forget what it was called.
Believe me, there is no easy way. No matter what you find it will take you awhile to get it working correctly and it will still come out weird unless you're only using 1 AVI file and don't care about the chapter skip. Even then, it's a pain in the butt
It's a lot easier to just buy a DVD player that will recognize and play AVI files on a DVD. If you want the DVD to work in any player, you're going to need the "author your own" method that I just told you was a huge pain in the ass.