steps don't work to add mobile number to message on MAC

Hi dbsfo,

Thanks for using Apple Support Communities. It sounds like you would like to send and receive text messages from your Mac. Right? In that case, you will need to set up message forwarding from your iPhones that messages can appear on your Mac. Guidance below can walk you through that and is from Forward SMS/MMS text messages from your iPhone to your Mac or iPad - Apple Support.

"Automatically forward texts to your other devices

1. Make sure that you're signed in to iMessage with the same Apple ID on each device:

• iPhone or iPad: Check the Apple ID shown in Settings > Messages > Send & Receive.
• Mac: Open the Messages app, choose Messages > Settings (or Preferences), then click iMessage. Check the Apple ID shown.

2. On your iPhone, go to Settings > Messages > Text Message Forwarding.

If you don't see Text Message Forwarding, go to Settings > Messages. Turn off iMessage, then turn it back on. Tap Send & Receive, tap Use Your Apple ID for iMessage, then sign in with the same Apple ID used on your other devices.

3. Choose which devices can send and receive text messages from your iPhone:

4. If you choose a device that isn't using two-factor authentication for your Apple ID, a verification code appears on each of your other devices: enter that code on your iPhone.

As long as your iPhone is turned on and connected to Wi-Fi or a cellular network, new SMS/MMS texts can be sent and received on the devices that you added."

At that point, if needed, you can select your number using the guidance from the article you previously reviewed, Add or remove your phone number in Messages or FaceTime - Apple Support. That may not be necessary though after going through the process mentioned above.

All the best.