I see that your site is created on our legacy builder - https://app.imcreator.com/. Unfortunately there's no way to add SSL to any site created under our legacy platform.
What you can do is create a new site under our new platform - http://www.imcreator.com/. Once you'll do that we'll be able to transfer the domain and license to the new site and add the SSL.
Please see how it's done -
First, make sure to create your XPRS account and XPRS site (we cannot transfer an IMC site to XPRS). Once your XPRS site is ready, let us know, and we’ll move your premium license from your IMC site to your XPRS account.
Make sure to send us the following information:
A) Your IMC username
B) Your domain name
C) Your XPRS username
D) Your XPRS site's name or VBID