If it doesn't come with the Setup and specifications guide printed, (Optiplex 7080 used as one example), it can be found online at the Dell site.  Either Google something like "dell optiplex 7080 setup guide" or "Dell optiplex 7080 documentation" for all docs on it.
What are your best recommendations for setting up a new Optiplex Desktop? For more questions regarding this contest, please visit the Information Page here.
DS 07/22: What are your best recommendations for setting up a new Optiplex 
Desktop?