OctaGate Switch™ can easily be run on the same computer as your web server. However, they can't use the same port. Typically web documents are served on port 80, so you will want OctaGate Switch™ to be listening on that port. If you allready have a web server on the computer you're installing OctaGate Switch™, chances are that the web server is allready listening to port 80. You must change the web server so that it listens on another port (port 5001 for instance). Once you have done that, you must add an OctaGate Switch™ domain that forwards incoming HTTP traffic (port 80) to your web server (port 5001, in this example).
You may want to make the domain the "default domain for the port" - this means that all unmatched incoming requests on port 80 will be forwarded to the domain. See here for more information.
See domains for information about domains, or The First Domain for a tutorial on creating domains.