When you book a flight with Spirit Airlines, you will have the option to choose your seat during the booking process. If you don't choose a seat at that time, Spirit will randomly assign one to you at check-in.

Keep in mind that Spirit Airlines charges for seat selection, so if you want to choose a specific seat, you will need to pay an additional fee. The cost of Spirit Airlines Seat Selection varies depending on the seat you choose and the route you are flying.

If you want to change your seat selection after you've booked your flight, you can do so by logging into your account on the Spirit Airlines website and selecting the "manage travel" option. From there, you can view and modify your seat selection.

It's worth noting that Spirit Airlines does offer some free seat assignments, such as exit row seats and seats at the back of the plane. However, these seats may not be available on every flight and may be assigned on a first-come, first-served basis.