iMessage is an integrated messaging application for all users of the Apple ecosystem. From your Mac, you can send a message to all your friends using the iPhone and, if you also have one, to send and receive regular SMS with Android users.
How to configure messages on your Mac
You do not need to use iCloud (or even an iPhone) to use iMessage, but you will need an Apple ID. If you already have an iCloud account, the email you used to sign up will be your Apple ID.
Launch the Messages application from the Dock, your Applications folder, or by searching with the Command + Space key. If you launch the application for the first time, you will need to log in. If you do not have Apple ID, you can click "Create a new Apple ID" at the bottom to sign up. Otherwise, sign in with your existing Apple ID.
Once logged in, open the Message settings by clicking "Messages" in the menu bar and selecting "Preferences" or pressing Command + Comma.
Under the "iMessage" tab, you will find options to manage your iMessage account. You want to make sure your phone number or email address is listed under "You can be contacted to receive messages to", otherwise you will not receive any messages on your Mac.
If you have two contacts, such as your Apple ID and your phone number, you can receive messages on both accounts. At the bottom, you can choose the one you prefer to use for new people messaging. Using an iMessage account by email means using an account over the phone. you can send a message to anyone using iMessage, even by their phone number. But only accounts based on the phone can send messages to Android users via SMS.
Before you close this window, you must make sure that "Enable Messages in iCloud" is enabled so that all your old messages synchronize correctly with your Mac. You will want to activate it on all your devices.
If your phone number does not appear in the email preferences, you will need to make sure that iMessage is enabled on your phone. Go to Settings> Messages on your phone and make sure iMessage is enabled. Otherwise, you will see "Use your Apple ID for iMessage" where you will need to click and sign in with the account you use on your Mac.
Once everything is activated, your phone number should appear in the Messages preferences of your Mac in a few minutes, after which you are free to use iMessage as you please.
If you want to send and receive SMS – this will allow you to communicate with Android users and anyone who does not own Apple iMessage – you will need to enable the transfer of text messages to iPhone alsoand link your Mac and every other connected device.
You will need to use FaceTime if you want to make audio or video calls. FaceTime is a separate application but presents a installation process.