How do I change the mail fetch option on my iPhone 7 plus

Go to Settings > Mail > Accounts like razmee said above but then click on Fetch New Data > Turn Push to ON (green) and also make sure that the Google account shown below is set to Push, not Fetch.

If you are running iOS 10, the option is now just "Mail".

Settings->Mail->Accounts->Fetch New Data

Devdogs17 wrote:

Trying to change the mail fetch option and google tells me to hit mail,contact,calendar and there is no such option

settings - mail - accounts -