How to Send a Message from Your Phone Number on Apple Messages

Desktop

1. 
   Open the Messages application.
2. 
   Click on Messages. It's in the upper-left corner of the menu bar.
3. 
   Click on Preferences.
4. 
   Click on Accounts. It's at the top of the dialog box.
5. 
   Click on your Apple ID. It appears in the menu on the left side of the dialog box. Enter your Apple ID and password if you're not automatically logged in.
6. 
   Click on the "Start New Conversations From" menu. It's at the bottom of the dialog box.
7. Click on your phone number. Now, new iMessages will be sent from your phone number rather than an email address.