To upload content, go into the media tab.

At the top of the menu there is a button with an up arrow icon. Simply click it and upload from your computer to add elements into the media drawer. You can also drag and drop content directly onto the Pages/Media Drawer area without having to use the upload button. This method is particularly useful for uploading a group of assets. A progress bar provides status on the files being uploaded, once complete they will appear at the top of your media drawer.

How do I add page next and back footers? What does it mean to drag-and-drop content?