In its infinite wisdom Apple has, in recent versions of its OS, made it MORE DIFFICULT to install software. How? By changing your Mac's security settings, so that third party software (such as Isaac) can't be installed easily.
Fortunately this is an easy thing to correct.
Do the following steps on your Mac BEFORE STARTING THE ISAAC FOR MAC INSTALLATION PROCESS:
1) Download Isaac for Mac
2) Double click on the download. A pop-up window will appear
3) Drag-drop the Isaac for Mac icon into the Applications icon
4) Go to your Applications folder. You will find Isaac application there
5) HOLD DOWN THE "CONTROL" key on your keyboard, then click on the Isaac icon. A new pop up window will appear
6) Now, move your mouse over the "Open" option. The word "Open" will be highlighted
7) Now, click on "Open" to start the installation process
8) There are three files that need to be installed: Isaac program, NI Visa drivers, and SI Labs drivers
9) After Isaac installs, you will get another pop-up window, for NI Visa
8) Follow the same Control-click-open method to install NI Visa
9) If, during your driver install, you see this message, click the "Not Now" button:
9) You'll next need to restart your computer. After the restart, launch Isaac. You'll next see the SI Labs driver window appear.
10) Follow the same Control-click-open method to install SI Labs drivers
11) After the SI Labs driver installation, you will need to restart your computer one final time