Is there a tutorial on how to apply items-icon?

[last inlet]

I'm trying to apply the items configuration shown in the photo, so I would appreciate it if you could tell me how. I'm using Items adder. Is it possible to use it by drag and drop? If possible, which folder should I add it to?

[neat belfry]

If your custom icons are all set in game, you can use the /mcpets editor command to place them where you please