i cant directly say where as gbatemp rules but forbid it "ill be dammed if this is not a big enough hint" Download
HERE make sure they are for your 3ds's region
dont use rxtools 2.6
for this process use rxtools 2.5.2 as devmode(rxtools) is required to update systemnand
if you try this without devmode you will brick your 3ds (devmode was never implemented in rxtools 2.6)
you will also need this version of sysupdater
https://github.com/profi200/sysUpdater/releases
i cant find the link i had to the guide but its outdated anyway so. . .
Best you can do is use sysupdater, here is a safe way how:
1)Install sysupdater in your system nand
2)Get rxTools 2.5.2 from rxtools.net
3)Get the 9.2 update from some iso site and place the updates folder in the root of your SD card.
4)Launch rxTools it in Dev Mode
5)loadsysupdater
6)Press A to update
all cfw solutions offer cia support now (save for ntr wicth you run ontop of other cfws anyway) here is a guide you can use
[Tutorial] How-to install a CFW on a 9.0-9.2 N3DS without CN/OOT
the beat way requires your 3ds to be on 9.2/9.0 systemnand its as simple as turning on the consoles power (once setup) and heres one on the auto-boot process
RXtools CFW coldboot full installation guide for New3DS, from Browserhax & Homemenuhax to Rxtools