Accessing your Google Drive offline is easy. In fact, it's a default setting for Drive to be available offline if you are using the "New" Google Drive. But to you may want to check to be sure. Offline access is device specific. If you have multiple devices you will need to do this on each device.
Steps to check Offline access for the New Google Drive:
1. Access Google Drive click on the gear and then settings.
2. Check to make sure Offline is checked and click done.
3. Your documents will now be available offline. You can edit and create while offline. As soon as you access drive with a WiFi connection, your Drive will sync.
Steps for setting up Classic Drive for offline. (Why is anyone still using Classic Drive?)
1. Access Drive. On the left side select More.
2. Then select offline. You will need to have the Chrome Web App for offline access to work. Download app if necessary and then enable offline access.