Final answer:
The next step when using the AED after it detects V FIB is to administer a shock to the victim's chest.
Step-by-step explanation:
When the AED detects ventricular fibrillation (V FIB), the next step is to deliver a shock to the victim's chest. The shock is administered by the AED through the attached pads. The shock is intended to restore the normal rhythm of the heart. Before the shock is administered, it is important to ensure that everyone is clear of the victim to avoid any injuries.