Integrate Bluetooth control to an existing Arduino code, how difficult?

I have a fairly long code which works on an Uno, it's a led lighting controller that runs up to 16 channels via a PCA 9685 pwm, it's displayed on a 16x2 LCD and controlled via a rotary encoder (I didn't write the code, it's open source)

There's quite a few menus and sub menus. My question as a non coder (last time I coded was in 1986) is how difficult is it, will I need to add lines to the Arduino code? I don't want to get in over my head, though I'm willing to give it a shot, the actual app building doesn't look too taxing.

I'm going to watch some more tutorials in the meantime.



The most important part is to understand how the data flows through the code.
From there, study how the timing (if any) works.