1. Download Moonshell, and unpack the files onto your micro sd.
2. Download BatchDPG, and use it to convert the movies you want into the format the Moonshell will read.
3. Put the fully converted movie into your micro sd.
4. Turn on your DS, and click on Moonshell.nds.
5. Click the movie, and it should run by itself.
6. Have some fucking patience before tripple posting. If no one answers your post, at least look around for similar topics, since this question's been asked so fucking many times.....
Lastly, this is in a wrong section.