When young cats get sick, they need extra attention.
Usually, if the mama cat is around in your kitten's life, she will do most of the work as intended by nature.
However, if you got your kitten from a shelter or a pet store, and especially if there is no other older cat around, you will have to do most of the work yourself.
So, it is important to research and read up as much as possible about kitten care before getting an especially young kitten.
Below, I have enumerated some key tips and tricks in order to get you started

• Between 4 to 8 weeks of age, kittens start weaning and begin to consume real food.
  They still like to cuddle up to their mommies for warmth, comfort and safety.
  
• If your kitten is by itself, then you will be required to provide the cuddling and your kitten will snuggle up to you to get cozy.
  It is therefore important that you do not have any cat related allergies because you will have to spend a lot of time in close quarters with your sick kitten
• Cow's milk is generally not recommended for kittens.
  They require special milk formulated for their digestive system which you can pick up at your local pet store.
  
• Cats are very clean animals and will lick themselves to get that way.
  Mother cats will lick their young in order to teach them this habit.
  A Cat will however, instinctively learn this habit by itself if she is alone.
  If your kitten is not cleaning herself, then you should consult a Vet.
  

Please remember that the Vet is your special friend.
Sick kittens that have been estranged from their mother need extra care.
Always monitor your kitten for unusual behavior and do as much research as possible before getting a new kitten for your family.
Remember, it is just a little baby and requires as much care as a human child.
Be responsible.