I asked for clear, feasible instructions I as a beginner can follow or code samples.
If it's step-by-step instructions you're after:
Understand what the software does.
Review the code until you understand how it does it.
Decide how you want the behaviour to change.
Decide the simplest way to change the design to achieve that behaviour.
Implement and test the change.
Repeat as necessary.
If you can code in C# then you will probably find it quite easy to follow what the C++ code is doing since these two languages have a lot in common.