This instructions are about godaddy free SSL which comes with new godaddy server packages and based on my experience godaddy dont give this info straight-forward on a single call.
After few calls (spent few hours on this calls) i came to know that there is an easy option to just click the button to assign SSL to a newly added domain.
So though of sharing….
Go to 
click 
find SSL/TLS Status on the options available and click it
click Run AutoSSL button on it to assisn a SSL to your new domain added.
You need to re-click this buttom every 3 months based on the date mentioned (as pasted below) to keep using the free SSL.
In case you have a sub-domain added, go to DNS setting page of the domain name and make sure the sub domain is available as “A” record. If not please add a new “A” record for your sub-domain name.