Why won't my BodyPosition Work?

Nice try, but not quite! First off, you got the syntax for CharacterAdded correct, however not for when the player enters. I edited your code, and take a look at it:

game.Players.PlayerAdded:connect(function(p)
	p.CharacterAdded:connect(function(c)
		spawn(function()
			while wait() do
				workspace.Navi.Wing.BodyPosition.position = c.Head.Position + Vector3.new(0,2,2)
			end
		end)
	end)
end)

Let me explain it step by step:

1.) PlayerAdded Event calls upon anonymous function when a player enters

2.) Next line tells compiler to call upon CharacterAdded function when character spawns in

3.) spawn is a neat little built-in method that deals with coroutines. In a quick summary, it's almost like making another script to handle what you want. This means that you will have one script handling the bodyPosition each time the character spawns. While it's terribly uneffecient, it still works.

4.) while wait() do will obviously constantly loop and set the BodyPosition

5.) I added + Vector3.new(0,2,2) to make the fairy stay near the shoulder area, because if you set it to the heads position; it would be stuck inside the head.