How to upload google spreadsheet in "Spreadsheet to form" widget?

In the Spreadsheet to Form Widget, how do you upload a Google Sheets document?  It seems that I can only upload an Excel file located on my hard drive. 

Hello gouldca,

Unfortunately it is currently not possible to upload google spreadsheet in "Spreadsheet to form". I would suggest you to please download the google spreadsheet in your local computer and then upload it in the widget.

Thank you!