Event tracking code to Freeform generated form

Question

Running Expression engine v2.1.3.. I know we should update..

I have to say that I am not a developer, but I need a small help here. I have been asked to add a tracking code to a form.

This code:

onSubmit="_gaq.push(['_trackEvent', 'ClientA NO Landingpage', 'Button', 'Call me']);"

To this form:

{exp:freeform:form
   collection="Ring meg"
   notify="[email protected]"
   required="phone1"
   form:class="ringmegform"
   return="{if user_language != 'no'}{user_language}{/if}/aktiviteter/ringer"
   output_json="yes"
   ajax="yes"
}

This form uses the default template.

Any idea how I can do this?