To book a trip with multiple destinations, you can use the option "Multi-city" on the booking page.
You can use the "Multi-city" option if you are thinking of traveling through two or more cities without returning to your departure city. You can only book up to 2 flights using this option.
You can also use this function to book a stop-over: simply enter each step of the itinerary separately. For example, to book a stop-over in Venice on a journey from Palermo to Nantes, enter "Palermo" and "Venice" in the first group search fields, and "Venice" and "Nantes" in the second group. Bear in mind that when you select this option, you are booking two independent journeys without any connection between the two, and you must collect your baggage and check it in again when you reach the stop-over destination.
Finally, you can also use this function to book two separate flights that do not have any destination in common.