downloading nds roms on a mac

Hello (first post)
i have a mac computer and i'm trying to down load games onto a r4 ds. i already have put games on it from another website with no problem but they are not as up to date as romulation
my question is:
i down load the nds rom (on the download screen) i click on the file pic, a thing pops up saying.
open dictionary unable to read the dictionary of the application or extension bc it is not scriptable.
so i click on the (Q) to the right of it to bring up the file so i can place it on my desk top..
my question is.. am i missing a step bc when i place that onto the r4 ds micro chip in does not work or even so up on my ds.i looked on youtube and found a vid but the after the guy downloads it his mac does something diff by already placing on file onto his desktop...
thanks for your help..any help will be great i'm new to this kinda computer stuff (new to mac world for sure)

The NDS roms on this site are compressed using WinRAR.You need to extract the file from the compressed file. I believe WinRAR has a MAC version, you can find it at www.rarlabs.comIf not, I think there is a program called Stuff It that works with RAR and works on Macs.
http://www.stuffit.com/mac/index.html

thank you so much i got it to work www.unrarx.com was the site