No Response Message

When users are submitting our contact form, the form is not giving the user a response message indicating that the form was sent successfully. After users push the submit button, all of the information is still listed in the contact form & there is no pop-up response message showing up to let them know that the message did send successfully. This is turn creates users pushing the submit button SEVERAL times & we receive their form submission 1, 2, 10 times.

How do I get the contact form to clear all fields & have a pop up appear when users push submit letting them know their information was sent successfully?? I tried putting the [response] at the end of the code in the form tab but still nothing appears.