How to get the values from a form submission in a Wordpress widget

I've created a widget with a form and Submit button in it.

However, I don't know what should I put in its action attribute.

<form action="">
  fields here...
</form>

If nothing is written I never know on what page the user has put the widget so that I could get its values.

Do I have to send them to a template? This sounds logical as I need a template that will show all the results from the submission.. bu how can this be achieved?

It's second day since I've been searching for an answer =\