Tub, warm water...
Infants should bathe in an infant tub or a toddler tub with infant insert (generally a mesh swing that fits inside the toddler tub).
Use warm water (not hot!) and gently wash the infant with a soft washcloth. Use nonscented baby soap/shampoo. Work from cleanest to dirtiest body parts and after getting them all soapy use warm water to rinse them off. Immediately wrap in warm towel after bath.