Read How to redirect website HTTP to HTTPS using .htaccess

Note: Backup your website in case of something wrong.

Login into your cPanel

Use the file manager in cPanel to edit .htaccess file.

Now to put this code in the .htaccess file

RewriteEngine On
 RewriteCond %HTTPS !=on
 RewriteRule ^.*$ https://%SERVER_NAME%REQUEST_URI [R,L]

You can also redirect your website on the basis of port number

RewriteEngine On
RewriteCond %SERVER_PORT 80
RewriteRule ^(.*)$ https://www.yourwebsite.com/$1 [R,L]

Change yourwebsite.com with your website domain. This code will redirect all requests received from port 80 to HTTPS.

If you are not able to find .htaccess in your hosting then click on the Show hidden file.