How to load a fragment on button click in Kotlin?

If next button ID in the layout is "next" then you can make it like this:

val fragment = NextFragment()
next.setOnClickListener {
    supportFragmentManager.beginTransaction().replace(R.id.fragmentContainer, fragment).commit()
    }

Where "fragmentContainer" (which is FrameLayout view) is the layout ID of the container where your fragments will be placed.