How do I add an event to a goal funnel (Google Analytics)?

Question

Google Analytics

Hello.
There is a task to set up a goal sequence in an online store. It would seem that everything is simple. But I ran into the fact that I need to specify an event for the first step in the sequence, and not the page address.
Example:
Clicking on the "Add to cart" button (Event) → Cart (Page address) → Checkout (Page address) → Thank you for your purchase (Page address)

Answer 1

And if to use not event and "Virtual Pageviews"?
_gaq.push(['_trackPageview', '/shopcart.html']);