Once you've followed the other instructions to downloaded an installer from Perkin Elmer for the ChemDraw Pro software, follow these steps to install it on your computer.
After following the instructions for Downloading the ChemDraw Installer, locate the downloaded file in your Downloads folder -- it should have a name like 'cdpf170.dmg'
Find and double-click the ChemDraw Professional 17.1 program icon in your Applications Folder. At first run, the program will request your email address and the registration code for the software. Be sure to use the email address you registered with Perkin Elmer, and the Lehigh registration code, as listed in your email.