The add-ons your guests see at checkout on your website come from Guesty. To offer one:
- In Guesty, create the item as an Additional Fee.
- Enable the Booking Engine upsell option on that fee.
- Let it sync to your website, where it appears at checkout for the guest to select.
When a guest selects an add-on, it is added to the Guesty quote, paid with the booking, and shown on the reservation in Guesty.