Viewmodel hierarchy advice?

WPF application, MVVM design.  Each view has a VM.  Mainwindow houses all controls with their Visibility tied to each VM property IsVisible.

I'm having a hard time doing this without instantiating every VM as a member of the mainwindow's VM.  I need a pattern or framework to deal with it all, from the top.  If more detail is needed, I will provide, but I need some general guidance more than anything, I think, since this is my first go at MVVM and I don't have much expertise around.

Thank you!