First, let's make sure that you have the xcode commandline tools installed. In your terminal window, just type
xcode-select --install
If you receive the message
xcode-select: error: command line tools are already installed, use "Software Update" to install updatesall is well. You are good to go.
If, on the other hand, it tells you that you need to install commandline tools, then just let it do so. That should take no more than a couple of minutes and then you are good to go.
If neither of those things happen, you will need to visit the app store and download xcode. It's free. And no computer scientist should be without. Once that's installed, go back and try
xcode-select --installagain.
Now, please follow the instructions at Henry Walker's Grinnell site. You should do this in class or in a course assistant's helproom. The required packages include eSpeak, libjpeg, espeakPackage.2.0 and MyroC.3.1.a. All four installations are essential for a fully functional Scribbler so I would recommend you to follow all the instructions exactly.