Recording User Activity using Munchkin JavaScript

Hi Guys,

I'm working with Marketo for the first time and really hope someone here can point me in the right direction.

Currently I have some forms on my website that can successfully create leads in the Marketo database. These forms are sending data to Marketo via the REST API.
What I am now trying to do is capture the users activity, and associate that activity with that form submission.

After coming across this documentation:
Munchkin JavaScript API Calls

This is the understanding of how I think this should work (correct me if I am wrong)
1. When a user hits a page on your website, a cookie is created. (When you call  mktoMunchkin("###-###-###"));

2. As the user browses your website and does things like click a link you can record this actvitity in the cookie by calling for example

    mktoMunchkinFunction('clickLink', {
        href: '/MyClickedLinkONE/Story'
    });

3. Then after you submit the form you associate the activity with the submissions using the email address and this method

    mktoMunchkinFunction('associateLead', {
        Email: 'user@domain.com',
    });

I can see in the example on the documentation it also says you should supply some kind of key, the examples in PHP and I am a bit lots about how to do that?

I have tried to do these steps other than the key I just mentioned, I am still getting the form data into Marketo but I can NOT see the user activity.

I have also done the following:

In the head of all my pages (master page) I have added a reference to munchkin.js like this:

<script src="//munchkin.marketo.net/munchkin.js" type="text/javascript"></script>

and I'm not getting any errors in my browsers console.

Am I going in the right direction? Is there something that I am missing? any advice welcome