the covers are usually removeable and washable--air or low temp dry. the harness straps you'll need to read your manual, but I generally use a damp cloth to clean and then spray lysol or febreeze lightly after they've dried.
I have a britax and the carseat cover comes off and I pop it into the washing machine. With kids with food allergies and oral sensitivities, puking is/was a normal part of my day :/.
I hand wash and air dry. Never submerge the straps in water or use any chemicals or harsh cleaners on them. The sun is your friend when it comes to getting the smell out
There should be cleaning instructions on the cover- most say hand wash only or wipe clean only. I always threw them in the washer on gentle cycle then air dried...