Kitten Wont Eliminate

Hi, I'm new here. This is somewhat of an emergancy question. About three days ago I found an adorable female kitten in the middle of a street. I looked around for any signs of any other cats and found none. I decided to keep her, or at least until she's a little older. I have almost no knowledge of raising kittens or cats, and have visitied numerous websites for instructions. I understand the importance of having them expell after they eat, or at least once every day. She has not expelled since I got her. She seems about three weeks old. Am I to worry about this as much as I am, or should she be able to expell on her own when the time comes? I've tried a warm damp cloth every time I had finished feeding her with no result.

Does she eat on her own or are you bottle-supplementing her? At 3 to 4 weeks old, many kittens are ready to do things by themselves. Have you set up a litter box with appropriate litter for her to explore? How does she act when you place her in it? Does she make scratching/covering motions?

What is she staying in and by chance is she eliminating there? When I've handled orphaned kittens, I use either a cotton ball or toilet paper to stimulate them to go. I used a damp rag to wash them after feedings, and for some reason, they responded better to something that was smaller (like their mother's tongue).