You can install NSP files from an SD card, from your computer connected via USB, or from your computer over FTP. You can also install NSP files over the internet using something like HBG. If you choose HBG or DZ Tinfoil,
this version of Tinfoil is recommended since the official version now includes malware for Atmosphere users.
If you're going to use fusee-primary with emuNAND, you need to make the proper adjustments to the configuration files for it to boot the emuNAND. If you want to easily switch between emuNAND and sysNAND, you should use Hekate instead of fusee-primary.