Send Data from lora Gateway to a node (STM32l0)

I’m new to Lora and I’am trying to understand things and do some easy basic stuff,
First I built the Lora gateway using Rpi3 and ic880a module, then I tried to send some data to the gateway from my STM32l072Z and I did.
Now I want to do the other direction which is send from Lora gateway some data to the stm to do some work (ie turn on led) and let’s say we have multiple nodes how can I send to a specific node ?
I just need a glimpse of information that point me in the right direction, Thank you.

How you " send some data to the gateway from my STM32l072Z"? Which code you used? I’m facing issues

I used “STM32CubeExpansion_LRWAN_V1.2.1” which contain 3 projects, I used two of them , first the “AT-slave” project which is an example of an “LoRa modem that is controlled though AT command interface over UART by an external host” and the second is “End-Node” project which send periodically the sensor data (temperature, humidtiy …) to the LoRa network .