How to integrate form with existing google spreadsheet?

When I do this is creates a new Form to be sent to the Google Doc. I already have a Form that I would like to begin sending the incoming submissions to Google Doc. How do I do that?

Hello,

As far as I understand, you want to integrate existing spreadsheet to your form. Unfortunately, the integration, that we provide, will always create new sheet for the form.

I can suggest to check if you can use Zapier as middleman for the integration: https://zapier.com/apps/jotform/integrations/google-sheets 

Hope this helps! But, please get back to us if you need further assistance.