Open new window close the previous open windos in WPF/C#

Question

Hello Sir/Madam,
  I am develop a WPF Application.Home_Page.xaml page design all menu items.
but problem is click one menu item window will be open.then again click on another menu item 
that time previous open window not close.I want to open only Home_Page as parent page and
open anther page as child page.and in that child page open only one page at time.
Please Help Me.My Email [email protected]