You should arrive only within 5 minutes of the requested pick-up time.
If the booking is made for 1 pm, the pick-up window is 12:50 pm - 12:55 pm. This way you're able to meet the passenger in time for their pick-up without having to spend additional time waiting prior to the start of the pick-up window.
Do not forget to 'Activate' the trip once you start your way to the passenger.