To add a button that will appear in the app header, you need to define it in the Layout used by the view in question. The layouts are usually defined in index.html using data-role="layout" assignment.
If you want only some of the views to show a button and some not, then you need to define two different layouts - one with the button and one without. Then, go through your views and set the data-layout property of each view to the corresponding layout id.
You can see a sample which demonstrates a Home view using its own layout and two other views using a layout with a back button here:
Just note that the back button will not be functioning as expected in the Kendo UI Dojo. You can copy the sample code into a stand alone page or AppBuilder project and test it.
I hope this information helps.