Google Assistant is available for Android devices with Marshmallow and Nougat. If you've been waiting to get Google Assistant on your phone. There's a simple way to get it.

Follow the steps below to get Google Assistant on your phone
Go to your device settings
Language and input
Change the language to English (United States)
Download a VPN app from playstore for example (Stark Vpn)
Reboot your phone
Launch the VPN app
Select a United States server.
Then click connect
Launch Google play store
Then update your Google app
You should have Google Assistant on your phone
How To Launch and Use Google Assistant

To launch Google Assistant launch your Google app. Or long press on the home button
You will see a screen “meet Your personal assistant” tap continue
To allow the necessary permission Tap am in.
Yay! You just got your personal Google.
http://www.kemtechie.com/2017/03/How-to-get-google-assistant-android-device.html

http://www.kemtechie.com/2017/03/how-to-customize-google-assistant-settings.html