Google Analytic Event tracking code in a Landing Page or Form Button click?

Hello,

I came across in difficulties for inserting ga event tracking code in an Act-On landing page, specifically to track a form button click. I haven't tried it before, but I am not sure where to add this code. I am using Labs forms. 

I would greatly appreciate it if you kindly provide me with new suggestions or ideas on this.

Thanks
Vanesa