It's very easy! All you need is a browser and a CD/DVD drive.
Insert the disc into the CD/DVD drive. The drive should spin up the disk. It may automatically show you an Explorer view of the disc's contents. If not, it should give you some options of what to do next. Choose to view the files. An Explorer window opens to the drive. Double-click on index.html. This opens a page with automatic links to the units that exist on the CD/DVD.
If you wish, you can "install" the lessons by copying the contents of the disc to a folder on your hard disk. The name used by the download is JansCompLit101. That's it.
Using multiple products: If you purchase different products on disc and copy them to your computer, be sure to put them to the same folder structure. Then the links between units will work.