You can download PQSpreadsheet.mez from here. And save the file to Documents\Microsoft Power BI Desktop\Custom Connectors\ folder and restart Power BI.
Then you'll be able to see the connector within Other tab. Select the connector and copy&paste url of your precious spreadsheet file.
Finnaly hit the Sign in to connect to your Google account:
If Google cries about unsafety of this operation, just ignore it.
If you'd like to have (for security reasons) your own connector that would use just your's tokens use this tutorial.