How to change the symbology of the layer with python script in ArcGIS? [duplicate]

Question

Possible Duplicate:
Change Symbology of layers from within ArcMap

I need to write a script to change the symbology of the layer. I've read all the topics about symbology in ArcGIS-help and still haven't find the solution. I made my own symbol in Corel, imported it to ArcGIS then I made a layer file (.lyr)..

ArcGIS help says: " When a model is run from its tool dialog box, you can specify how model outputs are to be symbolized when added to the ArcMap table of contents. This can be performed in two ways:

Using a layer symbology file
Using the Apply Symbology From Layer tool"

So I need to do it by the first method. There is also topic "Setting output symbology in scripts" (I guess its nearly that what I'm trying to do). It says:

Set the symbology of the output.

#   output    = the output value
#   params[2] = the output parameter
#
params = arcpy.GetParameterInfo()
desc = arcpy.Describe(output)
if desc.shapeType == "Polygon":
    params[2].symbology = "c:/Tools/Extractor/ToolData/polygon.lyr"
elif desc.shapeType == "Polyline":
    params[2].symbology = "c:/Tools/Extractor/ToolData/polyline.lyr"
else:
    params[2].symbology = "c:/Tools/Extractor/ToolData/point.lyr"

I can't understand that. How to use it. The layer I want to change the symbology of is named "Three" so in the place of (output) I have to choose this layer... but what next? If I only have a layer with one kind of shape (point)

Can somebody help me? ( I have no idea about creating the scripts :) )