Hyz you have to download an official mod from the Steam Workshop (official because Valve created it :P)... It's "The fall of the space core" :D Once you install it, make sure it's listed and checked on the data files list (skyrim laucher)... Then you just have to make your way to the West Watchtower (west of Whiterun, where that dragon shows up and you find out you're dragonborn) and the Space Core from Portal 2 should land nearby... Then you can add it to your inventory, he's hilarious xD To create the helmet you have to take the Space Core to the Atronach Forge (in the midden, below the College of Winterhold), place him in the pedestal, put 1 Refined Moonstone and 1 Iron Helmet in the offering box and then pull the lever... Now you have both the Space Core (Spaaaaace) and a Dovahcore Helmet :D

How do I get a portal-core into Skyrim? xD