Google Analytics 4 will automatically track purchases as conversions. But, often, we want to flag a key event or two higher in the funnel as a conversion. Here's how to flag the add to cart event as a conversion in GA4.
Click the Admin gear icon menu on the left.
Click "Conversions".
As you can see, purchase events are flagged as conversions by default. To flag add to cart events click "New conversion event",
Enter "add_to_cart" and click Save.
You can see all available events in the Notion Google Analytics 4 template here.