Easy! Go to the Home tab and head to the date of your appointment, pick the consultation you want to reschedule, tap the 3 dots and reschedule your appointment. 

Alternatively, you can also find the appointment under orders within the Profile section of the app. 

Tap the appointment, tap see details and hit Reschedule consultation.

Please know that you can only reschedule the appointment up to 30 mins before the consultation time.