Show image for post

I have a static front page on my site and have categorised all my posts and used the category on the menu to link to the posts. I want to include an image for each post – the posts all have a featured image but it does not show. https://pics-elated.com/category/eventpics/

How can I get an image to be displayed please? I am a complete amateur so would be grateful if any replies could take that into consideration!