Google Assistant is built in for Android Nougat devices. To get them for Android Marshmallow and earlier, you need to do some settings for Google App and Google Play Sevices. Its pretty easy. Just follow these simple steps and use the latest Google Assistant for your device,
Google App and Google Play Services to the latest version available. You can do that via playstore itself. Link to update Google Play Services
- Set language
Change your device language to English (United States). This is because Google Assistant currently supports English (United States). This can be found in Settings=>Language & input=>Language. You can do a search for “Language & input” if you can’t find it.
- Time to clear up!
Clear cache for Google App and Google Play Services from your device Settings=>Applications. This is for those applications to refresh and update to the changed language pack.
Press and hold power button and Google Assistant would appear.
Sometimes you might want to assign Google App to home button. This depends according to your device. Most probably you won’t need to.