XPath Builder location?

[AWBUND1]

Probably a stupid question but I am new to Workbench. I have searched to see if this question already exists.

I'm in Process Designer view in workbench for a Process.

I double click on a Set Value item to bring up the Process Properties.

I expand Mappings and see the current Mappings.

I click Edit the mapping Data button and nothing happens.

I need to add a new mapping and searching Help seems to suggest this is done in the XPath Builder, but I cant find it anywhere? Do I need to install it as an add-in to Workbench?

Any help appreciated.

[AWBUND1]

Using Workbench 10.0.01 if it makes any difference.

[AWBUND1]

Additionally this is the screen I'm on:

http://help.adobe.com/en_US/livecycle/9.0/workbenchHelp/help.htm?content=000262.html

But I cant get Edit mappings button to work? Looks like it tries to execute something when I click it but nothing happens.

Also the error that I've found in the Workbench error log when you click the Edit mappings button is:

!ENTRY com.adobe.workflow.editor 4 0 2013-03-15 12:32:51.489

!MESSAGE Failed to set schema source!

!STACK 0

java.lang.IllegalArgumentException: Invalid absolute path:

at com.adobe.livecycle.workbench.common.service.internal.ApplicationManagerImpl.resolveResourcePath(ApplicationManagerImpl.java:346)

at com.adobe.livecycle.workbench.common.service.internal.ApplicationManagerImpl.getResource(ApplicationManagerImpl.java:283)

at com.adobe.workflow.eclipse.utils.template.ProcessTemplateUtil.convert2Document(ProcessTemplateUtil.java:194)

at com.adobe.workflow.eclipse.dialogs.XPathBuilderDialog.fillProcessTree(XPathBuilderDialog.java:1604)

at com.adobe.workflow.eclipse.dialogs.XPathBuilderDialog.createDialogArea(XPathBuilderDialog.java:1248)

at org.eclipse.jface.dialogs.TitleAreaDialog.createContents(TitleAreaDialog.java:155)

at org.eclipse.jface.window.Window.create(Window.java:431)

at org.eclipse.jface.dialogs.Dialog.create(Dialog.java:1089)

at org.eclipse.jface.window.Window.open(Window.java:790)