The offline functionality is still limited to Chrome and requires the Google Drive app from the Chrome Web Store. If you've already enabled the offline support and use it for documents and spreadsheets, you don't need to do anything.
This table shows which Google Drive features are available when you're offline and you use Chrome for desktop or the mobile apps for iOS and Android. You can sync any file when you use the mobile apps, but the editing support is better in the desktop Chrome. You can also install the Google Drive app for Windows and Mac to sync the files that can't be edited online using Google Docs, Sheets, Slides and Drawings.