Save ListView item in XML file

Hello dear all ,
Am still working on my first C# winforms application .
I populate a list view with data from a XML file .
My xml file is like this




   
     
       
       
     





am using the function in my document join

I need to do somthing but i dont know how I strart , it's possible to choose one or some item then when we clic on a new bouton we write this items in a new xml file ( similar to my XML file with only the items choosen )  or add them to an existed XML file ?  What is the easy way to do it ?  ( am really a big starter )


this function is important for my application , but i dont find somthing in the net to start with it

thank u all