You can't, because the text free app only works out to actual phone numbers, not other iPod touches. Thats Incorrect , You Have to Get Your Friends TextFree Number To Text Them !
You have to add it to your plan - Okay, I do not know who wrote this "You have to add it to your plan" comment, but it was a pretty retarded answer. First of all, if you were to add it to your plan...