Sign in to the application to start using Google Drive.
Open your Mac HD - Applications - Google Drive. Double click to open.
This window will open.
Click Sign in now
Sign in to Google Drive with your computer password
Type your username & password
The folders and documents you have created previously will be there.
Open your HD - Look for the Google Drive folder in the side bar.
Now you can drop and drag documents and organize folders from your computer in this folder. It will automatically back up to Google Drive on the web.