Your baby's skin is best kept clean and dry.
If you notice any dry areas, you can unscented, hypoallergenic lotion or oil on those areas.
For your baby's bottom, if you have reddened area, you can use zinc-oxide cream
otherwise, a little bit of olive oil is sufficient
You do not want to use any baby-powder on the baby's bottom
as baby can have breathing difficulties.
In terms of exposure to the Sun, you do not want to put baby in front of a bright window
where baby can be exposed to ultra-violet light
so keeping the baby in indirect lighting with a hat on at all times.
In terms of sunscreen, a baby under 6 months of age should not wear a sunscreen.