Hello,
What do you mean by IR file?
Regarding the gateway that @phileep pointed you just need to add your wifi and mqtt broker parameters, no needs to modify the IR commands.
-Set the parameters of wifi and mqtt
-upload the sketch into your esp8266
-put the IR diode with a transistor if you have
-subscribe with your borker to the topic home/sensors/ir
-press your remote control in front of the diode during several seconds
-record the code
-publish with your broker the code to the topic “home/commands/sendNEC”
-if not working try different send topics
Next step is the HA connection on which there is several subjects dealing with it.