Make sure that you have Apache Ant, a Java 8 or Java 11 JDK, and git installed. The required software is already installed on attu.cs.washington.edu, if you prefer to do the exercise there.
Clone the following git repository and read its README.md file: https://bitbucket.org/rjust/debugging
Test your set up by running ant clean test in each of the bug directories (i.e., in bug1, bug2, bug3). You will notice a test failure for each, but you should be able to compile the code and run the tests.