How do I link my iPhone to my ipad

This explains how to do it.

http://support.apple.com/kb/HT5538

Essentially what you have to do is to sign out of messages on the iPhone and the iPad. Sign in again on the phone first and when you sign in and setup messages on the phone, your iPhone number should be accessible to add to the iPad settings in Settings>Messages>Send and Receive at>You can be reached by iMessages at.

Thats not linked. That's pulling the same messages from a server to 2 devices. Why can't these things just talk to each other if they're both mine?