Need Help Getting Started

Hi all,
I'm a bit new to all this downloading etc etc.
I have downloaded some DS games for my daughter for Xmas onto a M3DS REAL but when I put the cartridge into the DS and it comes up that I need to put in the system file.....what is the system file and where can I download it.....can anyone help me pls??
Thanx

http://www.linfoxdomain.com/nintendo/ds/And don't use internet shorthand such as pls.