If you don't know what it is, click "Forgot your password?" then "Retrieve Customer Number". Then after you get your number, click either "Reset Password" or "Retrieve Password Hint".
If you are already in your DomainsByProxy account, check the box to the right of the domain and click continue.
I was refering to the domainsbyproxy control panel.
Got a response from them:
Domains By Proxy services cannot be temporarily canceled or disabled to display your WhoIs information publicly as this would invalidate our services for the domain in question.
If you know the login detail of your domainsbyproxy account you need to just login there and make off the privacy selecting the domain name. If you don't remember try out to find their mail about privacy which has been sent to you during the time of making that domain name private.
I don't know if they are still doing this, but each new GD purchase transaction would be assigned a new account number unless you specified one.
Consequently, if privacy purchases were made using different GD account numbers, this would result in having multiple domainsbyproxy accounts,
each requiring its own usn and psw.