You can't. DVD-R's require much more space and have much more layers than CD's do. You'll need a special program to convert your DVD into a CD usable movie file such as .avi or .mpeg. That's why CD-ROM drives cannot read DVD's
If you do not have any concerns about quality, you can save an ISO image to your hard drive and use a program such as Ashampoo Shrink and Burn to put it on a CD. In terms of time required and quality, the procedure is not recommended.