Default (Q) How do I flash a Boost phone to Sprint?

I have a Samsung Conquer that I have activated on RingPlus it is OK but it is a terrible phone the battery runs down easily I only use it to talk/text I previously had a Kyocera Hydro activated but they threatened to kick me off my free plan if I didn't switch to a Sprint device. The Kyocera Hydro despite having the same processor as the Conquer runs ICS, the battery stands by for a month, the speakers are good and loud...

What would I have to do to flash the ESN from the Conquer to the Kyocera Hydro to allow me to use it?