how to make windows app using kotlin

What do you mean by "windows app"? Do you want a desktop app that can run on Windows? Check out #tornadofx. Do you specifically want a native app using Windows specific APIs? I have no idea. Do you want an Android app all about windows? There's tons of tutorials on making Android apps (can't help with the windows part, sorry, not my cup of tea). Are you asking someone named "app" how to make windows? I'm not sure how Kotlin can help, but try #random.

I just download tornadofx plugin intellij idea and the git file was looking for fxml layout file but ther is no but I see integration with fxml file in tornadofx web pages