How do I baseline SQL Blocking?

Hello everyone,

On the Blocking tab of the SQL Activity page is a Compare option that allows users the option to select None, 1, 2, 6, 12, or 24 hours that is supposed to compare current settings to a baseline.  When I select any value, all I see is a blank screen which I _assume_ means that I don't have a baseline to compare to.  I've downloaded the Spotlight Help Viewer and searched for "baseline" and it explains what it is but not how to set it up.  Does anyone know of documentation on how to get this working?