1.) Tap the hamburger menu () in the upper-left corner,
then tap your name and email in the upper left.
2.) Select Add account
3.) Select Google
4.) This will bring you back at the Add your account screen. Here, enter your Gmail address and tap Next.
5.) Then, enter your Gmail password and tap Next.
6.) Select Agree on the Terms of Service page.
7.) If you want to add payment information, add your credit card here. Otherwise, just select No thanks.
8.) Once finished, you will be back at Accounts in Settings. If you want to see the accounts that you have added, or want to delete any, just tap Google.