This feature will be enabled by default so once it is December 16th, you can simply restart your browsers and you will be able to search for any Drive files that you have access to, including ones that haven’t previously opened in Chrome.
If you leave Drive file suggestions in Chrome enabled, users who are signed in and opted in Chrome sync will see Drive suggestions in the Chrome URL bar for their synced account. For more information about what sync settings users can manage and how they’re managed, as well as how to enable or disable Chrome Sync, see this article on Turning sync on or off in Chrome.
Partially reposted from Drive file suggestions in Google Chrome will be generally available beginning in December