How to add a G-Suite account to your iOS device

Logging in via iOS Device
1. Open Settings -> Mail -> Accounts -> Add Account -> Google
2. Enter your credentials
3. Ensure Mail is enabled and Calendars/Contacts if you want them synced as well
4. Once you press "Done" you will be able to access your mail via the iOS Mail App

For more in-depth instructions you can read the following article: https://support.google.com/a/users/answer/138740?hl=en