How do you get this?

I have been trying

You have to wait till ark ultimate survivor edition Halloween event happens then go to anywhere where rexes most commonly spawn and keep looking around until you see the rex ghost then kill it go into it's inventory and that's how you get the skin in ark ultimate survivor edition the island map and rexes can spawn on the dead island aka carnivore island and the mountains and the snow biomes including snow beach which is where you'll always find them