Before rescheduling, make sure you are doing so to the correct meeting and both attendees agree to the rescheduling of the chosen meeting. It is possible for delegates to reschedule their own meetings, so only perform these steps if absolutely needed.
Navigate to the Attendees tab and find your desired attendee, typing their last name into the Filter to find them quicker.
Click 'Schedule' to the right of the attendee's name, then click on the meeting you would like to reschedule.
Choose the 'Reschedule' tab and click the 'Reschedule...' button underneath.
Click on the new meeting time, making sure you choose the right date. 'Rescheduling...' text will appear on the time slot you are currently rescheduling.
If one or more attendees do not know about the rescheduling, type a message into the 'Optional message' text box alerting them of the fact. Otherwise, you may leave the message box blank and click the blue 'Reschedule' button.