This section of the guide covers how to open a class project in Eclipse. It is very important that you DO NOT simply open the class project: instead, you must import the project as a gradle project.
You should also make sure you're connected to the internet when performing these steps. When you're importing the project, Eclipse will automatically try and download some libraries you need to run your code.
First, download and unzip the project from the class website. You can find the download link on project specs page.
Run Eclipse. Select the "File" > "Import" option from the menu:
Select the "Gradle" > "Existing Gradle Project" option.
Hit "Ok" and "Next" until you encounter the below dialog. Click the "Browse" button:
Navigate to where your project is located and select it.
IMPORTANT: when you unzip the project files, you may end up creating two nested folders, both named "project1". When selecting your project, be sure to pick the innermost folder – that is, pick the folder that contains the "src" folder, the "build.gradle" file, etc...
For example: