In the blue navigation bar, click Add Content -->Default -->File.
In the Placement Folder field, make sure you have the correct folder selected. Consider placing all of your supplemental files (imagery, documents, etc.) into a separate folder, such as an "assets" folder, to keep things organized on your site.
If you need to upload multiple files then you'll need to follow the steps for creating a .zip file that are specific to your OS.
You can either "Choose" for the file or zip file on your computer, or drag the file from an open explorer window into the Cascade window.
The File Name will be the name of the file you upload. If you change the name of the file that is automatically generated for you, be sure you include the file extension (eg: .doc, .pdf, .jpg).
If it is a zip file, Click "Yes" then click "Unpack" and Cascade will unpack the contents of your .zip file into the location you specified.
Once you are done, you can click “Save & Preview” to create the file.