In CUSCO:

In plaza regocijo wait in front of the water fountain until the driver or a member of the staff call you name to direct you to your vehicle.

In OLLANTAYTAMBO:

Once your train arrive to Ollantaytambo Station you need to exit the station. The pickup will take place at the exit of the train station (in front of the exit gate). Wait until an agent will call your name to direct you to your vehicle.