Instructions for Windows™ Operating Systems
Select all the files you would like to upload and then right click on one of the files. In the contextual menu that appears select "Send To" and select "Compressed (zipped) Folder". The resulting ZIP file can then be uploaded.
Instructions for Macintosh™ OS X Operating Systems
Select all the files you would like to upload and then right click or hold the control key down while left clicking one of the files. In the contextual menu that appears select "Compress". The resulting ZIP file can then be uploaded.