How to change a user's login email

First, go to admin section under the “Users” tab:

Choose the user who’s e-mail you’d like to edit from the list:

This will open a window where you can edit the user information. You can change the e-mail address here, then click “Save Changes” to apply the update:

Then moving forward, this user can login with their new address! This will also send the user the following e-mail as confirmation: