From a Home screen, navigate: Apps icon > Settings > Accounts.
Tap Add account.
Enter the Gmail address then tap Next (lower-right).
Enter the Password then tap Next.
If preferred, tap Back up data to your device's apps, app data, settings and Wi-Fi passwords to enable then tap Next:
Enabled when a check mark is present.
If presented 'Set up payment info', tap Remind me later then tap Next.
To set up payment info after adding a Google account:
From a Home screen, navigate: Apps icon > Play Store.