Final answer:
The first step for using an AED after it arrives is to turn it on.
Step-by-step explanation:
The first step for using an AED (automated external defibrillator) after it arrives is to turn on the AED. This step is crucial as it activates the device and prepares it for use. Once the AED is turned on, the user will be guided through the subsequent steps, including applying the pads to the patient's chest, clearing the patient (ensuring no one is in contact with the patient), and ultimately, delivering the shock if necessary by pressing the shock button.