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`.
The openrndr-template depends on various packages including the core [openrndr](https://github.com/openrndr/openrndr/) and the [orx](https://github.com/openrndr/orx/) extensions. The version numbers of these dependencies are specified in your [libs.versions.toml](gradle/libs.versions.toml) file. If you want to learn about file format visit the [Gradle documentation](https://docs.gradle.org/current/userguide/platforms.html#sub:conventional-dependencies-toml) website.