<p>I'm trying to figure out how to consume a WCF service in BizTalk 2006 R2 (sending a request and receiving a response).</p>

<p>I've gotten as far as going through the "Add Generated Items" wizard.  Now I am trying to find out how to use the items it generated in an orchestration.</p>

<p>How should the request be made?</p>

BizTalk is overkill if you are just using it to orchestrate WCF services. You can use WCF services in .NET 3.5 inside of Windows Workflow Foundation a bit more easily.
That said, here is a screencast that should help:
http://www.pluralsight.com/community/blogs/aaron/archive/2007/11/15/49172.aspx