They'll be soft, blobby white things for around 2 weeks, during which they can't eat and can't really move properly. They use stored nutrients during this time.
After this time they will begin to moult to 2i. Don't feed straight away as their exoskeleton won't have hardened. Leave it several days to a week, when the babies begin to leave the mother and wander around, and then offer food. You can either give them appropriately sized prey, or larger pre-killed food. The mother may also catch food and offer it to her young.