The stack window is displayed using View|Stack. The stack window lists the stack frames, i.e. the functions that the program has entered, but not yet left.
The innermost frame (where the program currently executes) is shown at the top.
To switch to a different stack frame, simply click on that stack frame. The source window displays the source line where the function invocation took place and the local variables window and the watch window change to reflect the local variables of the selected stack frame.