You can use the UP and DOWN arrows on the right-side of the thermostat to temporarily adjust the current target temperature. You will see the "Set To" temperature in the upper right-hand corner update. The temperature will adjust by a 1 degree per arrow press if you are using Fahrenheit, or by 0.5 degrees if you are using Celsius.
In addition, this temporary adjustment to the target temperature will cause a "HOLD UNTIL" message to appear on the bottom right-hand side of the thermostat screen. The temporary adjustment will last until the time indicated under the "HOLD UNTIL" message, and then will return to your heating/cooling schedule.