When you select the Examine function, a helper object appears showing the X and Y values of the data point closest to the mouse pointer. The helper object displays the values whenever you move the mouse pointer across a graph, FFT, or histogram.

Choosing Interpolate changes how examine works.  If interpolate is on, and you do not have any linear fits or curve fits, then the Examine helper object will show the linear interpolation between the closest 2 data points.  If you do have any fits, then the Examine helper will show the value of the fit.

When you press the left or right arrows, the examine line moves to the left or right.  This can be a very useful way of explicitly examining a sequence of points in a graph with a large number of points.

Select Examine either by clicking its icon  on the toolbar or by selecting Examine from the Analyze menu.

Another way to quickly see values on a graph without creating an Examine helper object is to go to Graph Options and check "Mouse Position and Delta."  When this is checked, you will see the data value of the location of the mouse cursor in the lower left of the graph.  You will also see DeltaX and DeltaY displayed when you click and drag to select a region in the graph.