If you’re a Mac user with OSX 10.8.2 Mountain Lion or later, you can use the built-in Messages app to send and receive iMessages. Usually when you first set it up and login with your Apple ID it should pull over your iPhone’s phone number automatically, giving you the option to send and receive from your phone number by default instead of your Apple ID.
In case you got it setup with your Apple ID but don’t have the option to use your phone number, there’s an easy fix for you. All you have to do is logout of your Apple ID from the Messages app on your iPhone and log back in. Once you do, within a few minutes you should get a popup on your Mac asking for your permission to send/receive messages from your phone number associated with your Apple ID.
On your iPhone:
– Go to Settings > Messages > Send & Receive
– Tap Apple ID then tap Sign Out
– Tap Use Your Apple ID for iMessage, and log back in, then tap Next
That’s all there is to it!