Under the view menu select contour. In the dialog window that appears browse for the plt file just created for the shielding density. Press the import widget. The max and min for the data set now appear directly below the file name. Choose a reasonable value for the isosurface and do not choose a color.
Press apply and adjust the isosurface accordingly.
Once a reasonable value is selected for the shielding density browse for and import the current density for one nucleus. With the shielding density selected click on the mapping widget. Select the current density from the list. This will map the current density onto the shielding density isosurface. The range for the current density is specified directly after the isosurface value for the shielding density.