Custom serial device to send keyboard keystrokes

Hi guys,

I'm pretty new with Simhub. Been using it for a while with iRacing when the idea of making a button box came to me. I'm new to Arduino but I can understand coding. 

The problem I have is that my clone is not directly supported, since it has the ATMega328PB chip. However, using the custom serial device plugin I managed to read serial outputs from the board when pressing buttons. How can I bind those readings to specific actions, to emulate for example a keystroke on the keyboard?

Thanks!