I have raised kittens from that age.  Keep them warm, give them something to snuggle, feed them kitten milk replacement every 2 hours at first, then you can lengthen the time between gradually, as they get older.  I used a little bottle from the feed store.  After you feed them, wet a washcloth with warm water and stroke their tummies from the chest area down to the anus, as if it were a momma cat's tongue licking them.  This stimulates them to urinate and defecate.  Then you have to wash it off of them.  After the first couple of weeks or so, they should go on their own.  That is the time to start putting them in a litter box after each feeding to teach them that this is where they do that.  When they start to crawl around, just keep them safe and out of trouble.  They should be fine.  
 
The two I raised by hand were the sweetest most cuddly cats ever!  They thought I was the momma!  
Good luck!