It depends on how you set the pressurisation up but an easy way to stop the alarm is to click on the lamp.. this will cancel the buzzer. Scary isn't it.. it always makes my heart jump if I forget it's going to happen
Switch the Safety Valve to CLOSED (or NORMAL on the 510ED) before you take off.
The switch is next to the pressure gauge (overhead on the 510ED).
With Safety Valve closed (and RAM AIR closed) and the required cabin altitude selected, all should be ok.
The safety valve regulates the air pressure inside and it opens automatically to release any excess pressure.
If it's set open by the switch, pressure gets released and the cabin altitude equalises to the real altitude outside.
It beeps if the cabin altitude is above 10,000ft.