If you're new to the switch scene, I'd recommend looking around before posting a thread. There's nothing wrong with asking for help if you tried figuring things out on your own beforehand, but it doesn't look like you did that if you're asking a question like this.
To answer your question, there is a homebrew app known as tinfoil that allows for the installation of nsp files. It's easy to set up since most CFWs already have the right patches to use it. Again, you should look around a few threads before trying to set everything up.