How to Setup Mail Accounts and Sync Options in andriod

Open the app Email.
Enter Email address and Password, then tap 'Next' for verifying.
Leave 'Sync email form this account' checked, select other options you like, and tap 'Next'.
Enter your name to be displayed on outgoing messages, and tap 'Next' to finish.

After this setting, you can then open the app Email to send emails and read incoming mails, which are automatically synced with your GMail account over the air.