Before you can add anything to your CloudSite website you will need to be logged into your website editor.
For help logging in please follow this guide to Getting Started with CloudSite / FreeSite
Uploading images to your website.
First select Images from the left hand menu.
In the Images menu that opens select Add images...
You can either drag the images across or click Choose files and select your images.
As you can see the new image has been added to the list.