Its is five step process -
- Host with a dedicated IP address
- Buy a certificate
- Activate the certificate
- Install the certificate
- Update your site to use HTTPS i.e. migrate HTTP urls to HTTPS
While first four is pretty straight, for the fifth one use the following code in the .htaccess if you are using apache
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]