Everytime you feed her, you need to help her pee and poo till she gets older and can use the litterbox. The best litter to use is anything BUT scoopable because cats are very clean. When they do groom themselves they can swallow the litter which will cause a blockage and major problems. I recommend either Feline Pine or Yesterday's News. The best way to help her pee and poo is to take a cotton ball and gently stimulate her "down there" until she pees. She may poo as well. The more she eats, the more she'll start pooping.

Thank you for taking this precious baby in.