1 ) Open the mail.app application from the dock menu, alternatively you can find mail.app in the Applications folder.
2 ) If you do not see the "Welcome to Mail" assistant menu usually when
you first start mail application, choose "Add Account" from the
mail.app file menu
3 ) Fill in the Full Name, Email Address, and Password. The email
account password is saved in Mac Keychain, which allows you to
automatically login to the email account without having to re-type it
on mail.app launch.
4 ) Choose the Account Type POP, IMAP.
5 ) In Description box, You may give your email account a useful
description such as John's Sales Account. It's description can be
customized however you like.