You need to visit your website by typing https://yourdomain.com.au into your web browser. Don’t forget to add the “s” to the http part, that is what makes the site use the SSL certificate.
If there is a small padlock image displayed before your domain then SSL is installed. However it may say insecure but the SSL could still be installed. To check this you need to click the insecure word or padlock before your domain, some information will then appear saying if a valid certificate exists or not.