Wikidot handles images in a way somewhat differently than you may be used to. Rather than holding all of your images in one large file folder, wikidot attaches images to and files to the page they are used in. This may seem strange at first but it saves headaches.
Say, for example, you are creating a wiki about the Presidents of a country. Normally, you would have to name each portrait image as president-name-portrait.jpg. By attaching the images to the pages that they are used in, you can name them all portrait.jpg as each page has it's own images.
To add an image named photo.jpg and place it centre aligned in the wiki with a width of 500 pixels use the code [[=image photo.jpg width="500px"]]. The other options allowed include height, alt, title, style, class, size. The size attribute is very useful for flickr and locally uploaded images. If the image is attached to a page pagename different from the current page where it is being added, precede photo.jpg with pagename/. All attributes other than the image name are optional.