Hi zenkengee927b,
Thank you for participating in the Apple Support Communities. We understand you'd like to be able to answer FaceTime calls on your Mac. You shouldn't need to add your phone number. It should automatically be added when you sign into FaceTime with your Apple ID. This article explains more about this: Sign in to or out of FaceTime on Mac.
"To make and receive FaceTime calls and phone calls on your Mac, you need to be signed in to FaceTime with your Apple ID. See FaceTime audio and video call requirements.
To stop making and receiving calls through FaceTime, sign out of FaceTime or turn it off.
Sign in to FaceTime
You can use your Mac to make and receive calls when you’re signed in to FaceTime. You need to sign in the first time you open the app, or if you’ve signed out.
- In the FaceTime app
on your Mac, enter your Apple ID, then click Next. - Enter your password, then click Next to sign in.
- If you forgot your Apple ID or password or if you need to create an Apple ID, go to the Apple ID account website.
After signing in, you can choose a ringtone, turn on features such as Live Photos, and customize other settings. See Change settings."
Take care.