Hello,
I understand it might be a little hard in the beginning , if you are just starting to work with the NXP Wireless Connectivity stack with Bluetooth LE would strongly recommend you to check the training video series we have available in the web page so you can not only understand the basics of Bluetooth Low Energy, but also get a better idea of the stack structure.
To understand a little more about the beacon, you can check this community post where you can see it is well explained, it's a little old but the basic structure remains the same, we will try to update it soon.
We also have available a complete application note to help understand the use of Unique 40-bit MAC Address in the Wireless MCUs. Basically you will need to locate the ControllerSetBD_ADDR function in your project, still, I would recommend you to check the application note I mentioned you.
You can also check the custom profiles guides we have also available
How to create a Custom Profile - Client
How to create a Custom Profile-Server
Creating a custom profile using NXP BLE stack – Server
Regards ,
Estephania