Go to the address printed on the card, download the kernel files, place them on a microSD card, along with some .nds games (either in the root of the mSD or in a "games" folder). That's it.
If it doesn't work... Return it.
I had one just like yours and it was DOA. It was stuck in a white screen. And I'm not the only one. Many people complained that this card is a hit or miss, including the reseller. Then I exchanged it for a "R4i Gold Pro" that has a different website printed on it (but from the same reseller). Works just fine.
If yours says something about "Konami Digital Entertainment" or something like that on the homescreen of the 3DS, it's running the latest firmware. You don't need to update it (well, rather... you can't update it; there's nothing to "update" to). But you do need to download and place the kernel files on the flashcart's microSD card.
Nintendo stopped blocking DS flashcarts since the 6.x days.