1. If you wish to hide the featured image of a blog post in single view

Please add the code below to Customize > Additional CSS

.post-article .post-media {
    display: none;

Here is a guide how to add custom css: How to add custom CSS / PHP code or modify the theme code


2. Or you can simply decrease the Featured image size in a single project view:

Please add this code in the Additional CSS field:

.portfolio-image-wrapper .vamtam-responsive-wrapper img, .portfolio-image-wrapper img, .post-article .post-media .media-inner img {
    width: 700px;

Adjust the width number according to your image size.