How do you modify games directly?

[Nomzr]

As in, stuff like this:

https://www.youtube.com/watch?v=jFdkKtNXZWY&list=PLMHq_9wgaCklCW-pKEzUjDQ_DGKsoRO8l
https://www.youtube.com/watch?v=rHctqUI5RDU

Do you need a certain program to do so? I mainly want to mod Kirby Air Ride, tweak some stuff around. I understand there is a filesystem setting within Dolphin, but how would I know what each file actually is, and then how would I go about modifying it and saving it?

[Helios]

Varies from game to game. There is no one process that works for every game. You'll have to learn how the game you want to modify works and how to edit that game's files.

Perhaps looking for modding communities specific to the games you're interested in will help.

[Shonumi]

Apparently modding Kirby's Air Ride is a thing. Maybe give a shoutout to the guy in the video and he could give you some pointers.

Aside from that, apparently Kirby's Air Ride has a powerful debugger that you might want to look into -> https://tcrf.net/Kirby_Air_Ride/Debug_Mode

[Kurausukun]

I don't remember if Scrumpy posted the modded files or not, but if he did, you could replace the files in the ISO and then rebuild it with GC Rebuilder. As for the Melee one, that's just a Gecko code, as written in the description.