Create and manage contacts in Messages on Mac
You can create and manage your contacts right from Messages.
Create a new contact
You can create a contact card for the person you’re texting, if they’re not already in your Contacts.
In the Messages app
on your Mac, select a conversation.Choose Conversations > Add to Contacts.
If you see Show Contact Card instead of Add to Contacts, you already have a card for that person.
You may not be able to add contacts if you’re restricted by communication limits in Screen Time.
Fill in the fields in the contact card. Be sure to enter any instant message accounts you want to be able to use to send the person messages.
To send the new contact a message, type their name in the To field of the Messages window, or click the Add button 
next to the To field and choose them from the list.
Change how your friend’s name appears in the sidebar
If you only see an email address or phone number in the sidebar when you’re texting someone, you can open their contact card from the conversation and add their name, so you see that in the sidebar instead.
In the Messages app
on your Mac, double-click a conversation in the sidebar to open it in its own window.To search for contacts and content in conversations, click in the Search field in the top-left corner and enter what you’re looking for. Or, choose from the suggested contacts, links, photos, and more.
Hold the pointer over the email address or phone number in the To field, click
, then choose Add To Contacts.Click Contacts in the bottom-left corner of the window.
Do one of the following:
Search for an existing contact card for your friend, select it, edit the contact details, then click Update.
Select New Contact, enter the contact details, then click Create.
You may not be able to add or edit contacts if you’re restricted by communication limits in Screen Time.
If someone shares their name and photo with you in Messages, you can update that person’s name or photo (or both) in the Contacts app 
—just choose an option from the Update Contact pop-up menu at the top of the conversation.