So I followed the tutorial to make an item. I made the item ID : VikingHelmet. Saved the plug in. Loaded the game with the plugin. Went to console command and typed player.AddItem VikingHelmet 1 and then tried player.EquipItem VikingHelmet 1 both came up with nothing. WTF?!

May want to ask in the CK board.

You need to use the form ID to add things through the console. If you're still in-game, simply type

help "item name" 4

With "item name" being replaced with what you named the item (not its ID, but the name you put in to be displayed by the game). Your item should show up on there and you can use that number to add the item.

In the CK you can find the same thing in the item list next to its ID.

Note that if you look for the form ID in the CK that you'll have to expand the column, as its hidden by default.