If you have edited DV .avi files that you have captured to your PC you are going to have to do a bit further work.
The basic file format for DVD is MPEG-2. You are going to need to encode your files to this format & these files then need to be authored. DVD specs are very specific & the authoring process gives you the DVD navigation & makes sure that the files are laid out to DVD spec.
The prices of authoring programs vary from freeware to software costing tens of thousands of pounds.
A good place to look for free, cheap software & lots of advice on the processes required is
www.dvdrhelp.com
(RecordNow is a good burning (not authoring) program & DVDShrink is good for shrinking or re-authoring large projects so that they will fit on a DVD-R disc)