I am going to start by stating that you may not need to do any of this.  From you other post, I see that you have Import Agent.  I am guessing that you are using Import Agent to bring in the images and then trying to use Workflow to apply the template data from the XML.  It also appears that the XML is formatted for use with the ImportEngine.  Rather than having the image files imported by Import Agent, tell Import Agent to import the XML file.  When Import Agent grabs the XML, it will recognize it as a List Import XML file and will use the LF ImportEngine to then import the files as directed by the file.  As long as the <LF:fileref ref="C:\image1.tif" /> has the correct image path and the ImportEngine has permissions to the file, it should create the LF Document, apply Template and Field values, and import the images.

But if you still want to use Workflow to parse the XML, then you need to search the web for XPath tutorials and/or samples to learn the syntax.  Then you need to copy and paste the full content of one of your XML files into the Test Input area of the Read XML activity.  Then you can test using what you have found on other XPath sites.