Not sure what hidden support forum you're referring to (there's the House of Healing on these forums here, and I don't see any posts from you), but you can get support directly by emailing
[email protected].
To redeem one (from Doug Davison):
When you get to the point where you get transferred to Paypal to login, there is a link at the bottom just below the Login that says "Pay with an online bank account, debit or credit card, or Paypal Credit". If you don't already have a Paypal account, I believe this is the option you want to select. If you do already have an account, then you do the login stage first and then use the option at the bottom of the screen (before the Pay Now button) that says PayPal gift card, certificate, reward or other discount. Click the button that says Redeem and enter the coupon code from the gift certificate.