Just want to add here that I hand raised a week old kitten and shes doing fine today
. I'm by NO means any kind of expert in this area, but sometimes personal experience can be helpful as well
Kitty had to be kept nice and warm- she slept in a small box lined with soft blankets in a heated room- I also put a hot water bottle filled with warm but not scalding water, wrapped in towels on one side of her box in case she got a little cool ( I had to refill it with warm water at each feeding so it would stay warm enough). Sometimes she'd curl up to it, but she had the ability to get away from it if needed. She also enjoyed having a beanie baby to snuggle up to, I suppose it reminded her of her littermates.
I fed her every three hours, through the night as well and stimulated her bottom gently with a warm cloth after each feeding. Make sure the formula is the right temperature and that the nipple has a good flow rate. I had to enlarge the hole in her bottle a little as she had a hard time getting the milk out.
I also spent a lot of time lying on my bed with her and letting her snuggle up to me, I think she benefited a lot form the love and attention.
One thing people kept reminding me of was the chance that she wouldn't make it, and that I had to be prepared for that. However, don't let that possibility stop you from giving it your all. This kitty is lucky to have found you, good luck!!