no no, not that.
This is an old image, for when Shiny Necrozma released but PKHeX isn't updated yet. (So Shiny Necrozma appeared illegal, despite being legal. Because PKHeX has yet to update at that time, to include it).
That's the context.
Create a folder named mgdb at the same location where your PKHeX (not the shortcut, the main file) is located. (My PKHeX.exe is inside the pkhex folder)
Inside the mgdb folder, place the wonder card. Then boot up PKHeX. The event is now appears legal.