Q: iMessage setup on a new iPad air

Have an iPhone 4S with messaging from phone number. I got a new iPad air and it only wants to message from the Apple ID email address. It does not give an option to add a phone number, only give an option to add another e-mail address. I only want to message from the phone number. How do I sync this new iPad Air with the phone so that iPad will use the phone number too. Phone and iPad both have the same Apple ID