Use the Module Manager tool to directly install the extension from the downloaded file, for all extensions that support Module Manager. For vtiger CRM 5.0.4, the Module Manager is not included in the base installation and you need to download and install the vtlib Extension first.
It's wonderful
It worked out of the box.
As said in the manual it's a one way sync from Vtiger to Google.
It worked even for my professional calendar (@dottn.com) hosted on google
