• Go to the Switch eShop on Nintendo Switch.
• Then find Minecraft from the search bar.
• Now install the game and purchase it if you have not purchased it yet.
• After the installation process, launch the game and click on sign in with the Microsoft Account given at the bottom left on the screen of aka.ms/remoteconnect Nintendo Switch.
• Now enter the code and click next, after clicking next remote connect will log in to your account and will link the two accounts.

Via  https //aka.ms/remoteconnect