Ok thanks @lobothijau. I think the issue is you need to select a JDK installed on your machine for the Gradle JVM. You can do this by hitting the three dot menu next to that drop-down.
If you don’t have the JDK installed, you can install JDK 8 or later from here:
Install the JDK on your macOS system and then try to reopen the project. Once the project opens, be sure to select “Import Changes” on the Gradle popup that you see in the bottom right of the IntelliJ window.
At that point, once the Gradle syncing and build is complete, you’ll see a Run/Play button next to the main function definition. Click that to run the code.
Thanks again and let me know if that works!