The Google Search widget is usually on the home screen on any Android device, but if for any reason you have removed and looking for it, do as follows to add the Google Search Bar to home screen on Galaxy S7 and Galaxy S7 Edge:
1. Press the Home Button to go to the home screen
2. Tap and hold your finger on an empty space in the home screen to open the Edit mode (You can also pinch to zoom out while on the home screen)
3. Press the Widgets button on the bottom of the screen to add a widget to your S7's home screen
4. Swipe between available home screen widgets and find the Google Search widget
5. Tap on the Google Search widget to see available widgets, which are: Google Now and Google Search.
6. To bring back the Google Search Widget to the home screen of Galaxy S7 (Edge), press and hold on the Google Search widget and drag and drop it on the home screen. (Make sure there is enough space for a 4x1 widget)