In Linux/Wordpress Hosting :
FREE SSL certificate will be automatically activated within 48-72hrs of account activation, domain addon or subdomain creation.
You have to redirect your domain from HTTP to HTTPS through your .htaccess file. You can add this code to your .htaccess file or ask your developer to do that.
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
OR you can use
cPanel >> Domains >> Force HTTPS Redirect
In Windows hosting follow :
https://hosting.india.to/clients/knowledgebase/223/Steps-to-enable-Letandsharp039s-encrypt-in-Plesk.html
free ssl certificate, SSL