I'm sure there is one but I don't have a link at the moment..
With that said, the installation of a second instance is the same as the first, you have to have a new IP address and a new server net name and probably an instance name. If you installed SQL before as a default instance you will be required to specify an a named instance name. It will need new shared disks.
I guess the question I have is what specifically is the question you have?
CEWII