Using Worksheet_SelectionChange() event macro

I saw following link regarding highlighting rows while in an excel spreadsheet.

http://www.mcgimpsey.com/excel/highl...iteRetainColor

It indicates to use a Worksheet_SelectionChange() event macro. Here is the code:

    Private Sub Worksheet_SelectionChange(ByVal Target As Excel.Range)
        Cells.Interior.ColorIndex = xlColorIndexNone
        ActiveCell.EntireRow.Interior.ColorIndex = 36
    End Sub

I can’t figure out how to use the code and I can’t figure out how to turn the code “on” to use it. Any help is appreciated as I am new to event macros.

P.S. once I figure out how to turn it “on”, how do I then turn it “off”?