Before you start working with Kotlin, make sure that the Kotlin plugin is enabled. The plugin is bundled with IntelliJ IDEA and is activated by default. If the plugin is not activated, enable it on the Plugins page of the Settings/Preferences dialog (Ctrl+Alt+S) as described in Managing plugins.
Kotlin support in IntelliJ IDEA
Kotlin support in IntelliJ IDEA includes:
Dedicated file type, denoted with .
File and Code Templates for creating Kotlin symbols, which allows producing the Kotlin classes , interfaces , enums and objects .
For details, refer to this tutorial.