how do I send text messages through messages on my computer to other iPhones?

The messages program on my MacBook Pro used to be synced with my iPhone messages. I could text other iPhones on my MacBook Pro and it would show to be my cell phone number.

Something happened that I am unaware of and now on the messages program on my MacBook Pro it shows my Apple id and not my cell phone number. How do I make it where my cell phone number shows on messages & not my apple id?