The Prism Commanding QuickStart - included with the Prism drop should provide the simple code example you are looking for.
All data-bindings go against the current DataContext unless specified otherwise. The DataContext is inherited down the tree of controls unless a control specifically picks a DataContext.
For example your Button might look like this and would look for the SaveCommand on whatever the DataContext has:
<Button Command="{Binding SaveCommand} />
Your button could also look like this if you wanted to bind to a command exposed on your classes code-behind:
<UserControl x:Name="UserControl">
...
<Button Command="{Binding SaveCommand, ElementName=UserControl}"
...
</UserControl>
Using DelegateCommand is just a way of implementing the ICommand you bind to and that should be visibile in the Prism QuickStart.