Hello,if you are on Android Oreo then Google Pay should be available to you by default without any need of installing anything. You can go to Settings-Connected devices-NFC. Then turn on the NFC. After that scroll down and you can find the Tap & pay option there. Enable this option to use Tap & Pay. Sorry I don't know if it was available for Nougat since I am using Oreo now. However you can try searching for 'Tap & pay' in the search bar above the setting app. Thank you.
Thank you for correcting my answer @Notiz. Yes you can use other services too with Tap & pay not just Google Pay.