image before post

Hi, I have a number of posts. You can see the test posts here: https://synforum.nl/dataproduct-2/. This site is under construction. Inlog: hans password is leusdenfort33. What is should like is to give every post on the page a thumbnail on the left site of the page. Is that possible? I tried to upload an image to explain what I mean, but it seems to me that uploading is not possible. I try to explain in words what I mean: image post excerpt image post excerpt image post excerpt kind regards Hans Hagmeijer