How create hack for cheat engine

You do not create a hack with cheat engine. You simply find pieces of memory in a game - like say a game where you have 100health, and you would find that piece of memory remembering that and you would then change the memory to thinking that you had 99999999999 health.
But you can only hack flash games.

Cheat engine has extensive tutorials and FAQS explaining what it can do, and how.