I'm not sure where you heard that you can get the Plan B for free. You have to pay for Plan B and it does not need a prescription nor do most insurance companies cover it. You just ask the pharmacist for it and then take as directed. Here is a list of places you can get it for a bit less versus your pharmacy. http://ec.princeton.edu/locator/concerned-about-cost.html
go to planned parenthood if you want it for free but if you're over 17 you have to buy it like at a cvs or other pharmacies. the ones i've seen go for about $ 55-60 but i guess it depends on what kind you get. good luck!