Where do I start learning to port Windows games to ARM Macs?

Start with a small game you can build and change yourself. Learn some C, make something like Pong with Raylib, then try building it on both Windows and your Mac. That gives you a manageable way to see what changes between platforms.

From there, try an open-source game. You'll need to get its libraries and other dependencies working too. A native ARM build may need changes if the game or its dependencies assume x86, and Windows-specific code may need replacing for macOS.

For a compiled game without source code, there usually isn't a straightforward way to turn it into a native ARM Mac game. Translation or emulation is a more practical direction, though it's not the same as producing a native port.

There are two problems to handle: x86 instructions need to run on ARM, and Windows interfaces need equivalents on macOS. Look into projects such as QEMU and FEX to learn how emulation and translation work. Don't assume either project alone will run a particular Windows game on a Mac.

Don't worry about picking the perfect porting project yet. Learn programming fundamentals first, then get comfortable compiling and debugging small programs. Games add graphics, libraries and platform-specific behavior on top of an already difficult task.

Once a small program makes sense to you, start exploring how machine instructions, operating system calls and executables fit together. That background will make the emulator code much less mysterious.