How do people submit there completed forms

You should click on "Publish" button to embed the given code in your website or you can share the URL of your form with people or share it in social platforms like Facebook. Then people will see your form and enter their information and finally submit their forms, you will get notified for each of submissions.

Hope it helps.

The above information is correct.  Here is a bit more detailed guide on finding your forms URL:

https://www.jotform.com/answers/668928-Where-can-I-find-the-form-URL-of-my-form

And more detailed information on how to embed your form to a webpage:

https://www.jotform.com/help/67-Which-Form-Embed-Code-Should-I-Use