If your website works correctly when you open it with the https:// protocol, that is a good sign. It usually means the certificate is installed and functioning.
What you probably want, though, is for the browser to mark the page fully secure. For that to happen, all content on the page must be loaded securely through the certificate.
A common issue is that most of the page is served over HTTPS, but one image, script, stylesheet, or other external resource is still loaded over plain HTTP. That is called mixed content, and it prevents the browser from showing the secure state clearly.
To find the problematic content, inspect the page source or the browser developer tools and search for http:// resources. Every time you find one, update it to https:// or replace it with a secure equivalent.
Once all content is loaded securely, the browser should display the site as secure.