Nintendo Switch Manual page 53

Adding a user
You can add a user to the console by opening
System Settings on the HOME Menu and selecting
User ⇒ Add New User.
Deleting a user from the console will also
delete all of that user's save data.
You can delete a user by going to System Settings
⇒ User and selecting "Delete User".
Adding a user
What is a Nintendo Account?
A Nintendo Account enables the use of My
Nintendo services and certain smart device
applications.
On the Nintendo Switch console, linking a user to
Deleting a user