Step-1: Uninstall WhatsApp from your phone or device.
Step-2: Obtain your target's phone.
Step-3: Find your target's phone's Media Access Control (MAC) address.
Step-4: Find your MAC address using the instructions above.
Step-5: Change ("spoof") your phone's MAC address to that of your target.
Step-6: Install and configure WhatsApp on your phone.
Step-7: Get the confirmation code from your target's phone.
Step-8: When you no longer need to access your target's WhatsApp account, change your MAC address back to what it was.