Hello Atilla,
As a first approach, I'd suggest you to take a look into some ZigBee simple demo projects:
ZigBee light Coordinator
C:\Freescale\Kinetis_BeeStack_5.0.0\examples\zigbee_HAOnOffLight\kw2x\frdmkw24\freertos\iar\zigbee_HAOnOffLight_frdmkw24_freertos_Zc_Rs
ZigBee switch Router
C:\Freescale\Kinetis_BeeStack_5.0.0\examples\zigbee_HaOnOffSwitch\kw2x\frdmkw24\freertos\iar\zigbee_HaOnOffSwitch_frdmkw24_freertos_Zr_Rs
Demo documentation:
Kinetis ZigBee Stack Demo Applications User's Guide - C:\Freescale\Kinetis_BeeStack_5.0.0\doc\KZSDAUG.pdf
ZDO states for network formation are managed in ASL_UserInterface.c -> ASL_UpdateDevice()