Set up Messages on Mac
If you have an Apple ID, you can use iMessage — a secure messaging service — to send unlimited messages to anyone who has an iPhone, iPad, iPod touch or Mac. Messages sent using iMessage appear in blue text bubbles.
If you have an iPhone with iOS 8.1 or later, you can also send SMS messages to any mobile phone from your Mac. Messages sent using SMS appear in green text bubbles. See Set up iPhone to get SMS messages on Mac.
Set up iMessage
In the Messages app on your Mac, enter your Apple ID and password, then click Sign In.
Make sure you sign in using the same Apple ID on every device. See the Apple Support article Use Continuity to connect your Mac, iPhone, iPad and Apple Watch.
If you forgot your Apple ID or password, or if you need to create an Apple ID, go to the Apple ID account website.
Choose Messages > Settings, click iMessage, click Settings, then select any of the following options:
Enable Messages in iCloud: Select this option if you want to store your messages in iCloud. See Access your messages on all your Apple devices.
You can be reached for messages at: Select the email addresses or phone numbers that people can use to send you messages.
See the Apple Support article Add or remove your phone number in Messages or FaceTime.
Send read receipts: Select this option so that people who send you messages can see when you’ve read them.
You can also send read receipts for a specific conversation.
Start new conversations from: Choose the email address or phone number that you want to use for starting new conversations.
This option is only available if you have more than one email address or phone number listed below “You can be reached for messages at”.
Note: This is the information that others see when you send a message. For example, if you have your phone number selected, conversations with others show your phone number.
You can also set up name and photo sharing and notifications (such as sounds and alerts).
Stop using iMessage
If you don’t want to see messages on your Mac, you can sign out of iMessage.
In the Messages app on your Mac, choose Messages > Settings, click iMessage, then click Settings.
Click Sign Out, then confirm that you want to sign out. When you sign out of iMessage, you no longer receive messages on your Mac.
Note: If you want to stop receiving messages sent to your phone number, deselect the phone number below “You can be reached for messages at”. See the Apple Support article Add or remove your phone number in Messages or FaceTime.