c++ is a compiled language. Even if this (?game? what is is it?) were programmed in c++, you could not see the source code, only the executable machine code, so you cannot just edit the program if this is what you are thinking.
Most games that support user modifications do not do it via c++, they do it via Lua scripting language or something like it. If the program provides hooks to allow you to inject your own code/mods, there should be some online info about how to do this.
If you are trying to hack it, c++ is good at that. But this is possibly illegal depending on what you are doing and its not trivial, it will take a couple of years to get good enough to modify a program that way.
ah, a robot builder kit...
adding to the above, many of these tools are C compatible and a few more have a custom C or c++ "LIKE" language. For example the very common aurduino controllers speak 'not quite c++'