I can’t login my gmail account

1. Go to Settings > Mail, then tap Accounts.
2. Tap Add Account, then select your email provider.
3. Enter your email address and password.
4. Tap Next and wait for Mail to verify your account.
5. Choose information from your email account, like Contacts or Calendars.
6. Tap Save.

If this doesn't work, download the gmail app from the app store.

Hope this answers your question.