what do i do to get games to work on dsi

I am very new to this and was wondering why i cannot get the games to work on the dsi. I downloaded a couple of them, i extracted them (they are now in nds format) and put them on a 4 gig sdhc card. i go to data management on the dsi and i cannot see the games. am i missing anything else?

Buy them.

i was looking to download them to save a few bucks as we are short on funds lately. what am i doing wrong in this process. thanks

yes, you are missing something important to play the games. a flashcart!!

it is not possible to play roms via the DSi SD slot.

flashcart? what does this do? how do i transfer games from the sd card to the dsi?

here is everything you need to know:
http://gbatemp.net/topic/278137-dsdsi3ds-hacking-faq/

to put it simply, a flashcart is a hardware device that goes in the game slot on the DSi and allows you to play rom files from a microsd card.