First you need to set the VI to Run When Opened (VI Properties>Execution). Then you create a front panel Boolean. On the diagram what you need to do is have some sort of idle state where nothing is done until the Boolean is pressed. It could be a separate while loop that doesn't exit until the Boolean is pressed, an Event Structure, or as part of a state machine. Look at the shippings examples Queued Message Handler, New Event Handler, Using Buttons for Options to name just a few.