Go to your username in the upper right corner of the page.
From the drop down menu in the lower left corner you will see the text "Become a Gold Member".
If you still want to make the purchase, click the "Become a Gold Member" button.
Note: If you have 20 WINGS in your wallet, they will automatically be charged and you will get your new status. If you do not have at least 20 WINGS in your wallet, you will be redirected to a new WINGS purchase.