You'll need to make sure you have WhatsApp downloaded on your second device.
We have a separate feature offering more detail on how to set this up, but once you have done it, you can have a primary phone and a secondary phone both offering up your WhatsApp chats, allowing you to send and receive from either device. It's now possible to have WhatsApp running on multiple phones.
If you want to know more about how to edit a WhatsApp message, we have a separate feature detailing everything you need to know.
