To be sure that the certificate has been installed correctly and working properly, as well as that your customers are certain a secured connection is enabled and it covers data transmission through your website, you have the following indicators:

• A padlock/tune icon available in the URL bar.
• No error messages/ warnings occurred when connecting through https://yourdomain.tld.
• A Site Seal provided by the Certificate Authority installed and visible.

Note : From September 2023, the padlock icon will be replaced by a tune icon in the new Chrome browser version. Google's reasoning is that secured HTTPS connections have become the online norm, not the exception, and no longer serve as a trust indicator. As such, the tune icon itself will not be a trust indicator but will provide detailed information about a website's connection and settings. So moving forward, when using a Chrome browser, the primary indication of a successful SSL certificate installation on a site will be the absence of security warnings :

To have all these factors boosting up your visitors’ confidence you need to:

• Install a validated certificate received from the Certificate Authority according to the instructions.
• Check installation of the certificate using one of these checkers: sslchecker, certlogic, SSLLabs.
  
• Make sure that there is an automatic redirect from http://yourdomain.tld to https://yourdomain.tld (if needed).
• Check that port 443 is open.
• Avoid displaying any insecure content here.
  
• Install a Site Seal following instructions.

You can find SSL installation instructions here.