Once the certificate is active, you must configure your website so it is compatible with the HTTPS format. To do this, you can modify the .htaccess file so that when someone clicks on http://www.domain.com, they will automatically be redirected to https://www.domain.com. You can see how to do this by clicking here.
In some CMS, such as WordPress or PrestaShop, there are plugins to make these types of modifications simply.