Note that the example above uses jQuery to trigger the function call, but you could trigger the function call using any method you wish.fbq('track', 'Lead'); - To track the lead event on the page. Like Thank you page after submitting the lead.
If you have the Thank you page after submitting the lead then you can paste this code on the page and it'll track it as a successful lead.
If instead you wanted to track a standard purchase event when the visitor clicks a purchase button, you could tie the fbq('track') function call to the lead button on your page, like this:
