@LameNobody yeah it works but in my view its not the easiest way.
@nintendogba
ok then microsd will be the card for the "r4 3ds upgrade Dual core real time save"
and the sdcard will be the card from your 3ds (may you will get a bigger one before you start)
01) download the gateway 3.2.2 version
02) put blue card GW_INSTALLER.nds into the mircosd
03) put the Launcher.dat into the sdcard
04) now put your r4 into the 3ds start it and execute the GW_installer. Follow the setup.
05) restart your 3ds and go to: settings -> other settings ->Profile -> Nintendo DS Profile
06) you will boot into the Gateway menu there you have to backup your nand first and turn the 3ds off (hold powerbutten 10 sec twice)
07) put your sd card into you computer and copy the created NAND.BIN save very well! as well as the hole content of your sdcard
08) put the sd card back into the 3ds
09) restart your 3ds and go to: settings -> other settings ->Profile -> Nintendo DS Profile
10) you will boot oncemore into gateway menü. but now select format emunand
it will ereas all your sd card and will create the emunand.
now you are prepared to follow the steps from
here
Edit: Lamenobody has right