how do i sync iMessage with mac and iPhone?

1. Set up text message forwarding
   1. On your iPhone, iPad, or iPod touch, go to Settings > Messages > Send & Receive. On your Mac, open Messages, choose Messages > Preferences, then click iMessage. Make sure that you're signed in to iMessage with the same Apple ID on all your devices.
   2. On your iPhone, go to Settings > Messages > Text Message Forwarding.*
   3. 
   4. Choose which devices can send and receive text messages from your iPhone. If you're not using two-factor authentication for your Apple ID, a verification code appears on each of your other devices: enter that code on your iPhone.
   5. 

You may need to use the same Apple ID on both devices.