...brought turtles from china town ?!?

brought 2 lil turtles from c street in ny...dont know what kind of turtles they are...there tiny the size of a quarter and have red marks on the side of there head...how can i tell there ..and the lady gave me these lil green pellets but i threw a few in and the turtles dont eat them...im planning to buy a larger tak cuz the one i brought them in is tiny and they look so miserable...what else can i put on there tank to make it homie for them...should i do something like half rock/sand have water ect...dont know NOTHING about turtles just brought em cuz they look so dam miserable!!!