Adding buttons?

I built one of these! And it even works! Yay!

The encoders that I am using have a click button in them, and it would be a shame to waste that functionality, so I'd like to add some button functions. After combing through the library documentation, I see that it will support a bunch of OSC commands, so that's cool, but I can't quite decipher where to insert some extra lines to add functions in the code.

At the beginning there are some #define entries where I would add the buttons, and these (I think) can be called whatever I want them to be.

Later, I see where the pins are defined and the mode set.

What I can't figure out is where the actual instructions are sent. I think the arduino is packaging OSC commands into a serial transmission?