Two things that fire at the moment of the buy decision
This lesson does two installs back to back. Trust badges and a sticky Add to Cart bar. Both work at the same moment in the customer's experience: the second they're hovering over the buy button on a product page, deciding whether to actually click it.
The two are independent. You could do one without the other. Most of your customers will be on a phone, though, so if you're short on time and only get to one today, do the sticky cart bar first. The buy button being visible on mobile beats every other change at this stage.