How can I allow users to edit their submission?

How do you enable EDIT FORM so someone can edit it after submitted?

I'm assuming you're talking about allowing your users to edit their submission (not the form per se) after they submitted it, correct?

If so, you can add the EDIT LINK either on the Thank You page or on the Autoresponder email they get after form submission.

Complete guide: How-to-Let-Users-Update-Their-Form-Submissions-at-a-Later-Date 

In case we misunderstood your question, just get back to us with a bit more info and a clearer description of what you're trying to do so we can better assist you.