Some cars come equipped with child seats already installed. To find cars with child seats, click on 'Filters' when you search for cars. Tick the 'Child Seat' option to see all cars that have child seats fitted.
You can see a car has child seats from the symbol in its description
Alternatively, you can bring your own car seat. You’ll need to make sure the car has the appropriate anchor points. Just contact the owner before you book to confirm. You can do this from the car's profile page.