In most cases, you would need to process the images to a size that displays appropriately on your website. There's several Image Processing software (such as Adobe's Photoshop) available that can help you achieve image resizing. To assist you with the correct image size relevant to your website, every care has been taken to indicate the size in respective templates in the WMS.
However, if your template does not display this information or you have any specific questions, please don't hesitate to contact WMS Support. This can be easily done by creating a Support Ticket (under the Help menu).