This video is a guide on how to add a Gmail account to a Mac and Mac Mail. The following steps are:

Step 1:Choose Apple menu, System Preferences, and then click Mail, Contacts & Calendars.
Step 2: If you have already added an account, click the Add Account button.
Step 3: Select an account type, In this example we are choosing Gmail.
Step 4: Enter your account information, and then follow the onscreen instructions.
Step 5: Choose the apps you would like to use with your mail account.
Do you want Chat? Do you want Calendars?