If you are looking at this from IntelliJ IDEA you can start by expanding the _project_ tab on the left. You will find a template program in `src/main/kotlin/TemplateProgram.kt`
To create runnable jars for a platform different from the platform you use to build one uses `./gradlew jar --PtargetPlatform=<platform>`. The supported platforms are `windows`, `macos`, `linux-x64` and `linux-arm64`.