In principle, you have to mux the pin as a GPIO pin and disable the reset functionality. Best if you consult the reference manual.
How to do this with Processor Expert or in general, see https://mcuoneclipse.com/2013/02/16/using-the-reset-button-on-the-freedom-board-as-user-button/ (using KL25, but KL02 is very similar).
I hope this helps,
PS: I recommend to use a 'safety line' and not remuxing the pin right after reset, otherwise you might have difficulties to access the device using a debugger.