Final answer:
A bystander should attach the AED pads immediately upon returning with the device while you continue CPR. The AED's verbal instructions assist with pad placement and the machine can automatically analyze and treat abnormal heart rhythms.
Step-by-step explanation:
When a bystander returns with an Automated External Defibrillator (AED) while you are performing CPR (cardiopulmonary resuscitation) they should begin attaching the pads immediately. The AED is designed to be used by laypersons and provides verbal instructions for correct placement and use.
CPR is essential as it maintains blood flow to the heart and brain, but when the AED arrives it should be deployed as soon as possible because it can analyze the patient's heart rhythm and deliver a life-saving shock to correct an arrhythmia or ventricular fibrillation.