What does ''Sign in with'' mean?

Applies to: Nintendo Account

This feature allows you to quickly create a Nintendo Account by using the information from a pre-existing social network account such as Facebook, Twitter and Google+, as well as Nintendo Network ID.

If you create a Nintendo Account using such a pre-existing account, both accounts will be linked and you can use the login information of the linked account to sign in to your Nintendo Account.

More about: Accessing the Account