Sorry to hear about the inconvenience. Kindly, please share your Site WP-ADMIN Login details in the Private Content field so that we can check this concern on your Site and help you out accordingly.
Sorry to say there is no direct option in theme settings to add the image here. Try to create a HTML Block and upload the image in the HTML and add the HTML Block in the menu. https://xtemos.com/docs-topic/html-blocks-usage/