Before you can start using these cheats you need to have a CFW enabled 3ds with NTR. This is a bit of a process but is relatively easier if you can follow directions. Just make sure not to update your 3ds to anything higher than firmware 11.0 you can check this by going to the settings menu. I don't know about your particular model.
If you are still on something lower than 11.0 then you can continue modding your 3ds here:
https://3ds.guide/
After that is done you can grab NTR from Nanquitas here:
https://gbatemp.net/threads/release-bootntr-selector.432911/
Once that is installed, you can start using these cheats on either your physical or digital copy.