(KarelJRobot.jar, objectdraw.jar and BreezyGUI.jar)
Download the JAR files you need from the class website: uzza.us/cs/java/JARFiles.html to a folder on your PC.
Then you need to set the CLASSPATH environment variable in Windows, which tells Java where the JAR files are located. Follow the instructions at this link to set the CLASSPATH:
On my PC, the JAR files are located at C:\Program Files\Java\jdk1.8.0_231\jre\lib\ext. Here is a screenshot of the CLASSPATH variable on my PC, showing the location of the JAR files: