That depends on several things. First off, will your dvd player play avi files? Many newer dvd players can playback avi files that use the divx or xvid codecs. If yours has this capability, and the files use divx or xvid, then all you have to do is burn the files to a disk as data. I recommend ImgBurn for the actual burning process, since it will set the file type for you. (ISO9660 + Joliet for avi files) If you have it set wrong, ImgBurn will ask to correct this for you. ImgBurn is free to download and use. www.imgburn.com
If your player cannot use avi files directly, then you will need to convert them to dvd-video format. There are a couple of good, free programs for this. One is DVDFlick, the other is AVStoDVD.
DVDFlick is probably a little easier to use, AVStoDVD can use a better encoder. For both of them you need to set the output as NTSC dvd-video, since that is what we use in the US. Both programs can be set up to burn automatically to a disk with ImgBurn.