You’ll need to have the application from playstore already installed on your device. Press down one of the already existing app icons then select home screen editing.
Tap the + sign in the upper left corner of the home screen and look for google in the search bar.
Tap google in the results and then select on the size of the widget you want to use.
Tap to add the widget at the bottom and it will now be added to your home screen.
Drag, to place it where you’d like it to be on the home screen then choose done to save your arrangement.