A little over a year ago the Google Assistant was launched as a Pixel exclusive feature then some months later it became available for any device running Android Nougat or Marshmallow but tablets running the compatible Os versions didn’t get it. However, starting this week Google is rolling out the Assistant to all devices running Lollipop and tablets too. You don’t need to do anything—Assistant will appear in the next few days provided you are in the US (English, Spanish), UK, India (English), Australia, Canada, Spain, Mexico, Singapore (English), Italy, Japan, Germany, Brazil, or Korea then the rest of the world would continue.
However, it’s only for Marshmallow and Nougat tablets —no Lollipop. Assistant will hit Android tablets over the next week, but only in the US with English as the default language.