You can try using
SUPER (FREE!!!) to convert your files to DVD compatable MPEG-2 (SUPER shows it as "MPEG II").
You can look at the Workshop
Project Settings to find the correct options (resolution, framerate, bitrate, etc) for a DVD compatible MPEG-2 file. Note that NTSC (North America) settings are different from PAL (most of the world) settings.
BTW - Making a DVD from a downloaded file usually requires lots of experimentation. If you have a "hacker attitude" it can be a fun challenge!

If you are a "normal person" it can be a royal pain!

There are many different formats, and many different variations (of both the video and audio file-components). And, you are usually dealing with a highly-compressed format which tend to be difficult to convert or edit.