I assume that you want to put the file on CD so that you can play it on a DVD Player.
If your DVD player is Divx compatible then just copy the avi file to the CD. Don't worry about the length of the movie as this is not relevant for this. It's the physical file size that's important.
If your DVD player is not Divx compatible then with only a CD burner you'll have to convert it to VCD & it might fit but I would suspect the quality would be quite poor. The guides that Geno pointed you to will help you do this.
To view a 90min movie in decent quality you'll need a DVD burner & dvd media & convert to DVD movie format. Again the guides will help.
We have guides here as well. Look in the Video Editing sofware forum, they're right at the top.