How to change 'current page'

Hi,

I am pretty confused on navigation between pages in Xamarin Forms. I am trying to implement the following:
When the app runs it should show a ContentPage. When a button in the ContentPage is pressed it goes to a NavigationPage. I do not want to 'push' anything to any navigation stack in this case. Also, the NavigationPage that I will display after the ContentPage is done is not going to be a modal window; I just want to set the current page to be a different page, but I can't figure out how to change the 'current' page.

Thanks,

Makani