Design novice

Can any advise how to assign a train whistle sound to a button please? I am 64y.o. and trying to learn how to program RoboRemo and Arduino to control a model train set. Too many grey moments to comprehend most of this.

I assume the train will generate the sound and not the phone, right?
How do you trigger the sound right now? Is it by pressing a button on the train?

My trains are an older type running on DC not DCC. I was hoping to have the train recording play via the phone. Things aren't going well though. I am having the devil's time trying to pair my BT module to my android phone. Having another go tonight. I think all this is way beyond me.