Foster Cat eye infection ?

I found a little cat and she has an infected eye. I don’t have money to take her to the vet, but I also can’t leave her in the street. I want to know what I can do to help her heal. Only one eye is affected. I have two other cats, and I hope it’s not contagious. I know that im asking too much question and that i need à vet to have answers but please if you have any information, share jt with me. Thanks a lot !