You are not estimating the parameters, you are specifying them. I think you want to plot the PDF for the normal distribution over the histogram. A simple customization is sufficient. If you view the histogram in the default vertical orientation, then use the X Function( Normal Density( x, 0, 1 ), x ); If you rotated the orientation then use the Y Function( Normal Density( x, 0, 1 ), x ); Right-click in the histogram frame box and select Customize. Click the + button and add the JSL.
You get extra points if you figure out how to determine the curvecolor, style, and width...