It says X is not a valid member of part? Please help.

local Brick = Instance.new("Part")
Brick.Parent = game.Workspace
while true do
Brick.Position.X = game.Workspace.Player.Torso.X
Brick.Position.Y = game.Workspace.Player.Torso.Y
Brick.Position.Z = game.Workspace.Player.Torso.Z

You cannot edit values of Position. You can just edit Position itself. And you forgot to say thatTorso.Position.Xand not Torso.X

local Brick = Instance.new("Part")
Brick.Parent = game.Workspace
while true do
Brick.Position = game.Workspace.Player.Torso.Position -- you forgot to say Position. X = X, Y = Y, Z = Z

As spongocard said, it wont work if you dont put an endand an wait():

local Brick = Instance.new("Part")
Brick.Parent = game.Workspace
while true do
	Brick.Position = game.Workspace.Player.Torso.Position -- you forgot to say Position. X = X, Y = Y, Z = Z
	wait()
end