I have this car seat but I don’t think I have any photos of him in it as a new born x
It may be worth looking at a YouTube video on the car seat by the manufacturer or something to check. There is a newborn insert (which, if new, should be in there already set up) and the headrest is adjustable so should be at its lowest. (Sorry, really hard to explain on message!!)
this may help? https://vm.tiktok.com/ZGdSqHU1j/
Have you got a picture?