For this tutorial you need a DS flashcard.The gateway blue card will work. Go to the download secion above and download the latest version of rxTools.dat
In your download there are a few files available, open cdn_firm.exe, this will download your firmware.bin
Copy both rxTools.dat and firmware.bin to the root of your 3DS's sd card.
Copy rxinstaller.nds into the root of your flashcard's SD card.
If you are planning to decrypt your titles, place slot0x25KeyX.bin aswell on the root of your sd card.
(Not provided in the downloads, google it).
You will need slot0x25KeyX.bin aswell on your device if you're using emunand version newer or equal to version 7.0.