You can change or add an email address associated with your account by heading into your "manage account" settings by clicking your profile at the top-right corner your Dashboard.
In the window that pops-up, navigate to the Email Addresses section.
To add/change your account email:
Click "Add an email address".
In the "Add email address" window, enter the email you would like to add to your account. You'll be sent a confirmation email to verify.
Once your new email has been added, click on it in the Account Settings page where you can set it as your primary email address. You can also remove any email addresses from here as well.
Your primary email address will now be your new username when logging into your Clarity account.
Please note that if you you'll only receive email communications from Clarity at the email address you've designated as primary.