Hi! How wonderful you were able to save this kitten! I know our kitten advisor will comment as soon as she sees this, but in the meantime..yes, do feed her. Try a can of Friskies Kitten Food, most grocery stores have this in their cat food aisle...or any canned food labelled for kittens (or there is a recipe for Kitten Glop that I know someone will post a link to for you). Give her a low small dish of water (i never like using large bowls until I'm sure a kitten isn't going to go fishing and land headfirst in the bowl)..something she can't fall into.
Yes....set up a litter box...you can use a low edged one that you feel the kitten can get into. Place the kitten into the box within 15 to 20 minutes of eating..it may help her get the hint, and that is usually when they need to go (from my days of helping "mom" litter train her kittens)...use an unscented litter...since the kitten may taste test it (even better would be swheat scoop or world's best cat litter, they are grain based and without prettily colored chemical deoderizing bits)
Actually, silly me...someone will post a link to a great kitten site...I'm not on my own computer, so don't have access to my notes (and my memory doesn't always co-operate!).
best wishes with this little one...are you doing temporary care or will you be keeping her?