iMessage connecting to Mac Air
I connected my apple ID, but my phone number didn't link with it in messages like it did in FaceTime. The messages are sending from my email... thanks in advance.
MacBook Air
In the Messages app on your Mac, use Messages' menu to go to:
Messages > Preferences > Accounts > Start New Messages From
... and set this to your phone number if it appears.
If it doesn't appear, see:
Link your iPhone number and Apple ID to use iMessage and FaceTime - Apple Support