Add Processing Page Access to Launching Page

In the page that initiates the long-running process, add code to instantiate and navigate to the processing page
as shown in the example below.  (Taken from Oracle Developers Guide)

import oracle.apps.fnd.framework.webui.OAProcessingPage;

public void processFormRequest(OAPageContext pageContext, OAWebBean webBean)
{
   super.processFormRequest(pageContext, webBean);

   // This example assumes a submit button named "StartProcess" initiates the long-running process.
   if (pageContext.getParameter("StartProcess")!= null) 
   {
     // Create the processing page and pass it the fully qualified name of the controller that
     // you created to launch the process.
     OAProcessingPage page =  new
OAProcessingPage("oracle.apps.fnd.toolbox.samplelib.webui.processCO");

     // The concise message is displayed in bold and should briefly describe the process.
     // NOTE: never hard-code text display values as shown here.  Always use message dictionary.     
     page.setConciseMessage("This is the concise processing page message.");

     // The detailed message displays below the concise message in plain text.  It provides
     // additional information about what's happening.
     page.setDetailedMessage("This is the detailed message which should explain what's happening.");

     // This is displayed in the processing page title.
     page.setProcessName("<Process Name>");

     // Forward to the processing page.  Note that the OA Framework assumes you
   //  are retaining  the root application module.  Since we haven't specified a different root AM on
     // the processing page, the OA Framework assumes it uses the same root AM as the launching page.
     pageContext.forwardToProcessingPage(page); 
   }
}