I still have no clear idea of what your question really is. But see if this old blog post of Bea Stollnitz cant help you to do what you want:
GitHub - bstollnitz/old-wpf-blog: A selection of posts from my old WPF blog.
Posts 39 - 41 and posts 47 - 49 contain information on how to stuff with the treeview.
Otherwise, just take a quick search here:
Find an exampl of what you want to do and get back to us for help when you are stuck again.