Hi Amal, I hope you're doing well!
If the application being developed is going to make use of the NXP BLE Stack, then some kind of RTOS will need to be implemented alongside the application. There are some existent RTOS that are already compatible with the KW36 family of MCUs, like Amazon FreeRTOS, or the custom built OS Abstraction component of the Wireless Connectivity Framework included with the Connectivity Stack.
This need for an RTOS is because the BLE stack needs to comply with the timing standards set by the BLE Specification, and the OS helps manage these timing requirements.
More information about these options can be read in the following documents:
<…\SDK_2.2.2_FRDM-KW36 - MCUXpresso\docs\rtos\Getting Started with MCUXpresso SDK and FreeRTOS OS.pdf>
<…\SDK_2.2.2_FRDM-KW36 - MCUXpresso\docs\wireless\Common\Connectivity Framework Reference Manual.pdf>
The SDK for the KW36Z can be downloaded from the MCUXpresso SDK Builder Website.
Please let me know if you need any more information.