How do I open a new fragment from another fragment?

Add following code in your click listener function,

NextFragment nextFrag= new NextFragment();
getActivity().getSupportFragmentManager().beginTransaction()
             .replace(R.id.Layout_container, nextFrag, "findThisFragment")
             .addToBackStack(null)
             .commit();

The string "findThisFragment" can be used to find the fragment later, if you need.

You should create a function inside activity to open new fragment and pass the activity reference to the fragment and on some event inside fragment call this function.

This is more described code of @Narendra's code,

First you need an instance of the 2nd fragment. Then you should have objects of FragmentManager and FragmentTransaction. The complete code is as below,

Fragment2 fragment2=new Fragment2();
FragmentManager fragmentManager=getActivity().getFragmentManager();
FragmentTransaction fragmentTransaction=fragmentManager.beginTransaction();
fragmentTransaction.replace(R.id.content_main,fragment2,"tag");
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();

Hope this will work. In case you use androidx, you need getSupportFragmentManager() instead of getFragmentManager().