On MacBook, how do i put my phone number for iMessages instead of my apple ID/email
Solution 1:
Open Messages Preferences (click Messages menu at the top-left of your screen and click Preferences) and choose the iMessage tab.
At the bottom of this screen will be a popup where you can choose what to compose new messages from.
If you don't see a phone number here, make sure you're signed in on your iPhone. Go to Settings > Messages and check if you're signed in or not.