To change the home page events image, scroll down the page until you see the featured image box in the left column. Click on the “remove feature image” link and after it has been removed, click on the new link that states to add a “featured image.”
You will then need to select the new image from the media gallery or a upload a new image. If you use a new image, the optimal image size is 466px by 488 px. These dimensions will match the other images in the home page sequence.