How do I set up link preview image for the website?

POSSIBLY RELATED:

• Change Facebook thumbnail
  https://www.adhesion.co.nz/blog/how-to-change-website-thumbnail-in-facebook-post
• Change LinkedIn Thumbnail
  https://www.linkedin.com/help/linkedin/answer/81310/customizing-an-image-and-title-when-posting-a-url-on-your-linkedin-page

This question doesn't appear to have anything to do  with Dreamweaver.  

When you post a link where exactly?  Please be more specific about what you're attempting to do and can't.  Also tell us the size and aspect ratio (height x width) of images you're posting.

I am not sure which image you are talking about. If I were to link to your site I would use

http://fastertrack.com/

no image involved.

Having said that, you should NEVER use oversized images for your web page. Normally you would place thumbnails that can be clocked upon to see the full sized image. That way, someone using a mobile device would not be penalised for viewing your site.