I need emulater help

I cannot get a ROM I downloaded from here to work on my emulater. The emulater is a SNES one called, Snes9x. The only reason why I really need this is I plan on buying one of those things to play ROMs on my DS so I also have, snesDS. So, will it work in that? And why is it not working in my current emulater? I have noticed ROMS from here carry the extension .rar and all my other ROMs have a .smc extension. Thanks in advance to those who can help!

.rar files are called archive files. This means that the files you want are inside the rar file. To extract them, you need to download winrar from www.rarlabs.com. Rar is like zip, it makes files smaller, only rar generally makes them smaller than zip does. We use rar so that the roms take up less space on our server, and so they take less time to download for our users.

Thanks!