Move beyond the bottom of column D to cell D103. Select the Formulas tab and the More Functions options in the Function Library group. This will cause a drop down menu to appear containing a list of available functions. Move down that list to MEDIAN and select it.
At that point a dialog box should appear in the center of your screen. It will display the arguments D2:D102 in the window labeled Number 1. It will also show the result of calculating the median based on the cells in that range. When you select 'OK', that result will be shown in cell D103.
The formula =MEDIAN (D2:D102) will also appear in the formula window.