To make Plot 1:
  Edit/Data Sets
    Right-mouse, click create new [by formula]
      Start at: -10
      Stop at: 10
      Length: 100 (number of datapoints, i.e., resolution)
      Set type: XY
      X = $t
      Y = sin($t)/$t
      Click AS (autoscale) button.
  Plot/Set Appearance
    Legend String: Sin(x)/x
  Plot/Graph Appearance (or double click at top)
    Click Display Legend (the default, I think)
    Title Plot 1

To make Plot 2:
  Data / Import / ASCII
    Click "silver.dat"
    Click on Read to Graph: G0
    Load as Block Data
    Click OK
    Pops up Edit block data
      X from column 2
      Y from column 3
  Plot/Set Appearance (or double click line)
    Symbol properties Plus, Color red
    Line properties none
    Legend string silver.dat
  Plot/Graph Appearance (or double click at top)
    Click Display Legend (the default, I think)
    Title Plot 2