The login email / username for an account cannot be changed.
If you have products registered on your account, you may log in to Usage Intelligence, go to the Administration page and under Product Settings click on Users & Permissions, From here you can send an invite to the new email address you'd like to use. An email will be sent to the specified address, from which you can accept the invite and register a new account which will have access the same product.
If you do not have a product registered on your account, you can create an account with a different email address and continue to use the new account.
If you have created a new account and would like to deactivate your old user account, please contact support.