First you will have to create a web application monitor. See my previous post on how to create a web application monitor in opsmgr. To add a recording to an existing Web Application object 1. Open the Authoring pane. 2. Expand Management Pack Templates , and then click Web Application . 3. Select the object to which you want to add a recording. 4. In the Actions pane, click Edit Web application settings . 5. Select the request from the list where you want the recording to be inserted. Recordings...(read more)

Read the complete post at http://scug.be/blogs/scom/archive/2008/10/18/add-a-recording-to-an-existing-web-application-object.aspx