The safety of a car seat depends on proper installation. With that, of course, you want peace of mind that you’ve done it right. Look for a child passenger safety (CPS) technician in your area. They can check to make sure you installed the car seat correctly and teach you how to install it in the future.
In the past, you could go to any fire department and they would install your car seat. That is not the case anymore, so instead look for a CPS technician near you.