Unpack it to whatever directory you want to keep your work in.
Rename “toyGraphics-starter-master” directory to the name of your project.
Install Java SDK. You need Java SE (Standard edition).
Install IntelliJ IDEA. The community edition is free and absolutely enough for you.
Start IntellijJ IDEA and click “File/Open” menu item and open your project directory. You should open the directory containing “build.gradle.kts” file.
Wait until IDEA finished downloading libraries and building the project.
Start an example
As an example, you have two working programs inside this project. They are inside “src/main/kotlin/myapp/” directory.
You can open any of these files by clicking on its name on the left panel. When you see the source code of the program, click the small green triangle on the left from “fun main”, and you see the program working.
To stop the program switch back into IntelliJ IDEA (Alt+Tab in Windows) and click red stop icon in the toolbar.