If you haven't already set up an email account in Mail, you might be prompted to add one when you open the app. If you're not prompted, or you just want to add another account, follow these steps:
How to set up an email account for the first time, or add another email account.
3. Some accounts, such as Google, might ask that you click Open Browser to complete authentication in your web browser.
4. Follow the onscreen instructions to enter account details, such as your name, email address, and password. If you're not sure what information to enter, please contact your email provider for help.
The Inbox gathers together the messages for every email account you added. If you added more than one account, you can click the disclosure triangle next to Inbox in the sidebar, then select a mailbox to see only the messages for that account.