if you use atmosphere read this
1) download the firmware you want and put it in a folder on the root of you SD card (google nintendo switch firmware and ChoidujourNX and you not should have problems finding them )
2) download the latest version of ChoidujourNX put it on the root of you SD card ( I personally recommend 6.2.0 as it has been the most stable for me but 7.0.1 is also good. )
3) turn on your nintendo switch, access the homebrew menu, open up ChoidujourNX
4)you are going to see a bunch of folders,. select the one with the firmware you downloaded and press the "choose" button
5) select the exfat version if you want exfat support , let it load and then click on :select firmware: then click on "start installation: when finished click reboot ( If you install Big games over 4 GB directly from your sd card I recommend exFat. if you use emulators such as retroarch DO NOT use exfat as it will corrupt your sd card )
6) boot using RCM method like you always do
and you should be done.
i cant post links to external webpages since its against the site rules and i cant upload the files because i dont know what firmware you want