Go to My Items > My Account to be taken to your personal profile page. This page contains your personal information and login details.
Click on 'Clear Notifications' in the top right of the page to clear the notifications from the speech bubble in the top right.
You can change your password, click +Add to add a phone number or email address, or edit your existing email address.
Please note that you'll need to use your new default email address to log in with.