This depends on how the file is shared with you:
1) Shared as link:
Unfortunately, Google Drive links cannot be accesses directly from another origin (like yEd Live) due to security reasons. In this case, you need to download the file and save it in *your* Google Drive. Then you can access it through Menu -> Open -> From Cloud (Google Drive).
2) Shared directly (as file) with your Google Drive account:
In this case, the file is available in the "Shared with me" section of your Google Drive account. This means you can load it from within yEd Live through the Menu -> Open -> From Cloud (Google Drive).