How do I help orphaned kitten??? PLEASE HELP.?

Yesterday, I found a stray kitten about 6 weeks old laying in rocks about to die, I picked it up wondering why the mother had abandoned the poor girl. Low and behold as I began washing her I noticed a huge tear at the crease of her right front leg meeting her back and appendage. I have no money, I don't want to let her go, and I don't know if she has more than that. I noticed that she moved slow but thought she could have been learning to walk or too starved. She eats and drinks now but is mal-nourished. It wasn't bleeding and I am not sure if it will be able to heal itself shut. What can I do? And as a LAST RESORT, do humane societies take kittens for free? What place does? Are there any products to help me at a Petsmart, Walmart, Petco? Is this natural for kittens?