Most hackers won't tell you how they make hacks, otherwise they lose their "customers" when you make a better one than them.
From another website, a hacker posted "You really need to learn c++ and gain some problem-solving skills.
In your DLLMain if the reason you get when injecting is DLL_PROCESS_ATTACH then create the thread to your hack function which runs your code.
I would start by using the SDK in your hack function to start making some hacks.
(CreateInterface and get the pointers for cvar, materialsys, engine, etc)".
tl;dr Use Google for info.