Your site is clearly hosted by siteground.biz so that's who you need to talk to. GoDaddy is your DNS host/Domain registrar, but not your actual website webserver host.
Siteground have given your website a default certificate named after the server it's running on but configuring a certificate specific to your domain is normally up to you. It looks like they have instructions here: How to Add an SSL to Your Site - SiteGround Tutorials