I'm sorry, but at the moment 3rd part SSL certificates cannot be installed on IM Creator sites.
If you wish to add an SSL certificate to your site, you can purchase it from the following page - https://checkout.bluesnap.com/buynow/checkout?sku3504224=1&storeid=371840
After your purchase is complete, just send us a message either by live chat (in the bottom right corner of your screen), or email: support@imcreator.com