I have a two-node Windows 2008 cluster (enterprise edition) on which I have
installed a SQL 2008 cluster (Enterprise Edition) with a single instance of
SQL in an active-passive configuration. We want to add a third Windows node
and up to three additional clustered instances of SQL to this existing
cluster. The documentation I have seen is not completelt specific, so I want
to make sure I will be doing this properly.

I believe that I need to first add the the third Windows node to the Windows
cluster through Failover Cluster Management, making sure it will be able to
access the filer on which the SQL databases reside, then run SQL setup on the
third node and add the node to the SQL cluster. Is that correct, or does the
SQL setup also add the server to the Windows cluster as well as the SQL
cluster?

Once I have added the third node, how do I add the additional SQL instances
to that SQL cluster?

Thank you very much.