Google Ads conversion tracking for different actions

Hi, 

I am trying to setup google ads conversion tracking on my website. I want to do this in a couple of ways, purchases and also when the 'add to cart' button is clicked. 

I cannot find where I would put this code as the cart button would not be triggered on the checkout page, like a purchase may. It would seem I can only track purchases, but I am hoping this is not the case. 

Website domain is www.panelinc.co.uk

Thanks, Alex