AutoSSL (Let's Encrypt) Certificates
AutoSSL uses certificates issued by Let's Encrypt, a free SSL certificate authority (CA).
Let's Encrypt does not provide any kind of site seal or badge, and here's their explanation as to why this is the case.
What we recommend is that you simply add some text to your site saying something like:
This website is encrypted using industry standard TLS (SSL) technology
You may wish to also include an image, such as a padlock or other image to depict security.
Other SSL Certificate Authorities
If you are using an SSL certificate from another Certificate Authority, for example Thawte, Comodo, Symantec etc, please refer to the email communications you received from them regarding a site seal.