If you use the script to embed the form, you can set URL parameters to capture where the users came from.
You should embed your form on your website and then, open the page that has the form embedded inside, and add URL parameters at the end of the page URL.
For example, if you want to share your website link on Facebook, you can share this link:
Where "source" is the ID of the field capturing value from the URL parameters. This way, you will know where the user who submitted the form came from.