Hi emmyp25,
Your Study Units are web-based, which means you must have access to the internet when opening them. However, you can save them to a PDF so you will have access to them offline as well. For this you will need Adobe Acrobat Reader installed on your computer.
First click the "Print" Icon at the top right. Type in the total number of pages in the Study Unit, so that it will include all pages; in this example it is pages 1 through 76. Then click print.
You will then have the option to "Save as PDF". You can change that option if you want to physically print the Study Unit out as a hard copy. A little tip would be to try using Google Chrome to save to a PDF or print; other internet browsers aren't as successful in accomplishing these tasks.
Hope this helps! Best of luck with your studies!