how do i turn off imessage on new macbook air

Just disable any accounts you have within the app's preferences.

Apparently you have to have ALL your OTHER devices(pads and computers) with iMessage OFF and disabled, if it's OFF ON THE PHONE, or texts will go to iMessage and NOT TO YOUR PHONE!!! I have missed many texts until I figured it out! They are all stored on the app on my MacBook!! I had upgraded to Yosemite, and it had turned on iMessage by default without my knowing it, so whenever I was using the laptop(or left it on and was away from it), I wasn't getting texts from others using iMessage on my phone!! Very bad. Thank you so much for instructing me how to turn it off on my MacBook!!