You can change your WePay Merchant Center Email and Password in the Security section of the Merchant Center.
To change your email address, use an email address that is not currently registered with WePay.
Change email address
From the Merchant Center menu, click Security.
From the Identity tab, click the Edit button next to the email address.
Enter your new email and click Update.
From the Identity tab, click the Edit button next to the password.
Enter your new password and click Update.