infant carseat safety

anyone have screenshots or anything to help with this? our hospital no longer educates you and I'm not really sure who or where I can go.

our little dude was born at 35 weeks so had the inserts in his car seat THAT CAME WITH IT so yes, safe. but hes starting to grow and Idk if I take the butt insert out first, or loosen straps or how tight they should be on an infant etc. i know more about toddler car seats but not infant.

no judging please. i just wanna make sure hes safe. I can't find any visual help online. just paragraphs.