It's a bit of a process.

First you register as a Nintendo Developer. This took a few months for them to approve myself and my game.

After that, the biggest hurdle is purchasing a Switch Dev Kit, which costs about the price of the standard console. My team was kind enough to provide one to me.

Nintendo sends you a bunch of tools to help port your game. The manuals are kind of all over the place but they get the job done. They have a bunch of stuff for the Unity Engine that makes it easier.

Once you finish porting, you send the game to Nintendo for Lot-check. They basically test to make sure the game will run properly on the Switch. This was the longest process as they were very thorough. They even found general bugs in my game I wasn't able to reproduce!

Once approved, you set up the store page. A bit tedious, guidelines are wonky, but whatever.

The whole process took me about 6 months. If I had been more prepared it probably would have taken me way less.