You can't use it on Sprint, it's that simple. What you're asking is like trying to run a Mac only program on a PC, or trying to tune in an AM radio station on an FM radio. It won't work.
If you want regular cell phone service, you'll have to sign up for it with either AT&T or T-Mobile. Or if Sprint sells a WiFi hotspot device, you could carry that with you and use Skype or some other VOIP solution. Otherwise, you basically have an iPod Touch with a camera.