In JMP, in your bar chart output, click on the red arrow next to BMI Category and from the pull-down menu select Confidence Interval, and then select .95.
You can "redo" an analysis after you update information. For example, suppose you subset your data to examine only Hispanic children. Toggle to your output window and use the red triangle next to Distributions and select Script > Redo Analysis. This will open a new output window that has the graph and confidence interval for only the Hispanic children.