How to add Google listing Thumnail

Site URL: https://www.peterleemagic.com

I know there is no built in way using squarespace but coding is all new to me and i don't know where to start to get a thumbnail in my google search listing

Do you mean like, the side panel that pops up  to the right of the search results for some websites? Are you talking about the icon at the top of the browser/or next to your site title in search results? Could you take a screenshot of an example search result that demonstrates what you mean?

I mean this small picture that appears when you search google. Thanks in advance for any help you can provide. 

I think it is blog post thumbnail. Google will probably use thumbnails, or a random image in the article.