Use the reset password page found here: https://login.veeam.com/auth/realms/veeamsso/login-actions/reset-credentials
If you don't recieve an email with directions on how to reset your password within 30 minutes, create a new account.
Each portal account is unique and tied to the email address for which it was created. It is not possible to change the email address of the account. You must create a new portal account.