Congratulations!!!
Yep, you are supposed to use the swimming noodle. You don't necessarily have to wrap a towel around it though(your choice). If you need to you can also tape two pieces of the cut noodle together to make the car seat level and then stuff it in the seat. You are also supposed to kneel on the seat while fastening the car seat buckle. This helps to keep the noodle even and the car seat level.
Christine