The first thing that you need to realise is that the commanding model in WPF is very unlike that in Winforms development. It also, confusingly, does not inplement the command pattern. It took me a while to get my head around the new model.
just hook up a click event handler, but this is the worst for re-usability. To implement what you want you need to to create a Command
(although there are ones "out the box" for common commands such as Copy & paste and Open). These represent the action that will be taken.
At some point in the visual tree prior to using the command, you need to create a command binding, this binds the command to the methods to be executed.
Finally you need to hook the command source (in this case, the buttons) to the Command itself.
All this can be done in XAML, but would take too long to explain here. MSDN has the usual over-complicated article here:
This looks more useful: