Go to https://app.thumbnailtest.com/settings/team

Scroll down to the Channels section

If you would like to remove a channel:

a. Click the red circle next to the channel you would like to remove

b. Click "Yes" in the confirmation window

To add a new channel:

a. Click the "Connect More Channels" button

b. Choose the email connected to the YouTube channel you want to connect.

c. Follow the on-screen instructions and click "Continue" to allow access.

Click on the "OK" button to finalize the connection.