Cheat Engine

[serpanoid]

How can I add license system after the program made with cheat engine easy trainer making and making it alrdy to exe file?

[Dark Byte]

put your license in the about text

[atom0s]

You can use a packer that offers a licensing system in it but most are junk and easily removed from an executable.

You'd be better off writing your own kind of system that requires an active internet connection and some sort of authing/login to your own server. Lot more details to go into something like this to make it actually secure but from the sound of it you are looking to potentially protect something someone else made.