RAR or NDS file?

I have a R4 and all my games are NDS files (from *read the rules*) . But I noticed the romulation games are RAR file. How do can I play it on my NDS? When I load the game to my R4 it doesn't appear at all. Help.

https://www.romulation.org/forum/index.php/topic,3880.0.html

umm, you open up with winRAR and the NDS files are inside, think of the .rar files as folders