You're gonna need to download rxTools, sysupdater cia, and the 9.2 update pack for your 3DS. Then you need to inject FBI over health & safety app using Rxtools, and then launch Rxtools devmode (Pasta) to launch FBI, install the sys updater cia and then finally use sysUpdater to update your system. I was in the same boat as you when I wanted to install arm9loaderhax, but this helped me a lot.
Also make sure you use devmode or pasta mode and not rxtools sysnand or else you will brick.
I would recommend launching gateway or decrypt9 and make a NAND.bin backup before doing this.
Good luck, and if you have any questions let me know.
