To add images to forum posts, users can utilize the "insert image" button or type the IMG tag with the image URL. Images are only enabled in specific forums, indicated by a status box at the bottom left when creating a post. If images are disabled, only the link will display. Users can also attach images via the "manage attachments" button, but this option is not available for quick replies. There is a suggestion to allow IMG tags in more forums to facilitate clearer explanations with visuals.