You can basically just copy and paste it, it’s just a specialized executable (.exe) file.

What people are mentioning about cracks and hacks are just fancy ways of saying “tricking the system”

Easy example would be an old game that came with a CD key like Diablo. All it did is check if the game was installed and a valid key has been put in previously. Cracks/hacks basically make the last step moot in one way or another. It’s really no different than if you used your friends key just…. Thousands of people using the same code (thus why a lot of the time you could not go online with these games since some games would do additional checks once connected to the internet)