Downloading the software
Adobe's Digital Editions/Download page has both Macintosh and Windows versions. There are also links to the apps for IOS and Android devices.
Installing the Software
During the installation process, you'll be asked if you want Norton Security Scan. Look for and UNCHECK the permissions box to avoid this additional software installation.
Authorizing the app
After downloading and installing the software, you will be asked to either create an Adobe ID, or to authorize your computer without an ID. The advantage to creating an ID is that content can be accessed across multiple devices. The disadvantage is that creating an ID leaves a record of what you have read.
After the one-time installation, future downloads from Ebook Central will automatically open in Adobe Digital Editions