store data from richtextbox to xml file

Question

i m trying to create ebook editor in vb.net i design interface in VB.Net and use richtext box for editing, now the problem is how to store the contents from richtext box to xml file.

Main problem is where to put the xml code

behind the richtextbox

or

Create a new xml file

and how to start the xml code.

Yours trully,

Fahad Khan