Even though You have an SLL certificate for Your website, your visitors will not use HTTPS while accessing your website by default. However, using your Control Panel, you can force all your visitors to always use HTTPS.
The easiest and recommended solution is to setup a Redirection from HTTP to HTTPS. To do so, access your Control Panel and navigate to your Redirects menu.
A new page should open. You can setup Redirections for Your website(s) here. Setup a new Redirection in the Create a Redirect section and leave the first line as it is by default, while in the second line change the protocol from http:// to https:// and enter your Domain Name.
IMPORTANT: If you do not have a valid SSL certificate installed, your website can become inaccessible due to this redirection. Make sure to verify your SSL is properly setup on your account by manually accessing your website with https:// to see if it works.