For Gmail App
Download the GMail App or
If you already have an account set up
on the Gmail app...click the picture
in top left corner.
Click Add another account
Choose Google
Type in your email address and password
Follow the steps to complete setup
**To edit an existing account, select edit account
For Mail App (iPhone)
Go to settings
Accounts
Add Account
Choose an account or Use another
account
Type in email address if you use
another account
Follow the steps to complete set up