In the Sales Hub section, click on a lead pin you have already dropped. Then click on the edit button (pencil with a circle). The Google Form can also be accessed by selecting the Web Connect button next to the edit button.
Fill out any lead information on the Lead Detail Page . Once finished, click on the Web Connect button (the 2 dots connected to one) to open the Google Form (you may be prompted to sign into Google). Fill out your form and submit. The submitted form will be available on Google Form.