There are two steps needed in order to create a secure URL for the custom control panel for your Reseller account.
Firstly, once you have decided the URL that you want to use, a CNAME record will need creating for the URL to point this to
cp.stackcp.com and this will then create the redirect required to load the login page. For example, if you want to use cp.mydomain.com as the address to login to the control panel you will need to create a CNAME with cp in the first box and cp.stackcp.com as the target.
Secondly, you will need to ensure that you have activated the free SSL for the domain (see guide
here). Once active that certificate will cover all subdomains so will kick-in no matter what URL set for the control panel as long as the first step above has been carried out.
Once those two steps have been carried out you will then be able to login using the required URL as a secure page.
