1. Login to the cPanel (http://yourdomain.com/cpanel or http://yourdomain.com:2082)
2. Under "Mail", click 'Email Accounts'
3. Click 'Change Password' next to appropriate email account
4. Type New Password into 'Password' field.
5. Confirm the password by retype into 'Password (again)' field.
6. Click 'Change Password' to save the new password or 'cancel' if you do not wish to change the password