To serve your App Engine application via HTTPS and HTTP on a custom domain, you must configure SSL for Custom Domains via your Google Apps account. Follow the steps below to activate SSL for your domain.

1. Configure a custom domain for your application(s) by following the steps outlined in Using a Custom Domain if you haven't already.
    
2. Sign in to the Google Admin console. 
3. Do one of the following:
   • In the classic Admin console, click Domain settings > General and scroll to the SSL section.
   • In the new Admin console, click Security > (show more) > SSL for Custom Domains.
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4. Enter the App Engine Application ID of the application you wish to have SSL-related charges billed through and click Enable SSL for App Engine Applications. All SSL charges from this Google Apps account will be added to the given applications bill.
   
   You can disable SSL for a particular domain and Google Apps account in both the App Engine Admin Console and the Google Admin console. See Billing and disabling SSL for custom domains for instructions.
    
5. You will be redirected to the App Engine Admin Console for the application nominated in the previous step. You may need to sign into the App Engine application if it requires a different account than used to administer the Google Apps account. Click Enable to activate SSL for the selected application.
   
   Once you have confirmed that you wish to bill all SSL related charges to this application, SSL for Custom Domains is now activated for your Google Apps account.
    
6. After being redirected back to the SSL page in the Google Admin console, you may add VIPs and SNI Certificate slots. See Configure SSL certificates for custom domains for instructions on adding SSL certificates and private keys.