If you have installed SSL certificate on your website, you can force redirect visitors to the secured HTTPS of your website to make secure.

Create a .htaccess file in your public_html directory, and add the following code in .htaccess file.

Code:
RewriteEngine On 
RewriteCond %{SERVER_PORT} 80
RewriteCond %{HTTP_HOST} ^(www\.)?coolexample\.com
RewriteRule ^(.*)$ https://www.coolexample.com/$1 [R,L]
If you already have an existing .htaccess file: Do not duplicate RewriteEngine On.

Note: These above instructions not apply to WordPress installed.