Bar chart labels aren't in Graph Builder until JMP 11. If you really need them, you can use the Graph > Chart platform. Here's an example in JSL:
dt = open("$sample_data/Big Class.jmp");
dt << Chart(
X( :sex ),
Y( Mean( :height ) ),
Horizontal( 1 ),
Label by Percent of Total Values,
Show Labels,
Bar Chart( 1 ),
Y[1] << Label Format( "Percent", 6, 1 )
);