Using WhiBal in both Lightroom and Aperture are very similar and straightforward.
Simply click on the WhiBal in the reference shot. Then select all the pictures shot in the same lighting, with the reference shot as the most selected. Then *sync* the WB setting of the reference shot to the rest of the *lighting group* using the sync button on the bottom of the develop panel (in Lightroom) or by using Copy/Paste to copy the White balance adjustment from the reference shot to the others.
This video shows how it is done in Lightroom. For Aperture and most other image processing applications it is the same methodology but with different clicks and keystrokes.