How to use Drive File Stream on Windows and MacOS
How do I use Drive File Stream on a PC (see below for MacOS):
To access your G: drive you open up file explorer to show all of your drives:
Shortcut: Press Windows Key + E to bring up the explorer window.
Or you can Click on the Start Menu on the bottom left 
Click on This PC on the menu: 
Your G: drive will be shown here (along with the X drive which you might have used previously):
If the window opens up the quick access menu, click on the 'This PC' option on the left hand column to show your connected drives:
NOTE: Anything you delete in this Google Drive folder on your computer will delete from your google drive as well!
Any files you open in Google Drive this way, will open in their native app, and when you save the changes, they'll automatically be saved in the same location (just like if the file was on your system).
How do I use Drive File Stream on a MacOS:
Open the Finder app on your mac:
Your Google Drive will be shown on the left hand column:
Now if you're in Word for example, you can choose to save your files to any folder/sub-folder within the 'Google Drive' folder on your system and it will automatically save to your Google Drive.
NOTE: Anything you delete in this Google Drive folder on your computer will delete from your google drive as well!
Any files you open in Google Drive this way, will open in their native app, and when you save the changes, they'll automatically be saved in the same location (just like if the file was on your system).