To download a single file, click on the file's name and launch it's detail page.
Click the 'Download' button found to the top right had corner of the page.
Downloading multiple files and folders
In the 'Files' section of your workspace each file and folder has a check box to the right-hand side of it's title. Check the box(es) next to the file(s) and/or folder(s) that you want to download.
After selecting your first item the blue 'Select action' button will appear. After you have completed your selections click 'Download' from the drop down menu.
Depending on your browser settings you may then be given the option to either save or open the files in Windows Explorer.