To use the XPATH Fetch Page module, first enter the URL of the site you want. By default, the module will output the DOM elements as items in the preview pane. You can optionally use the “Emit items as string” checkbox if you need the html as a string.
You can use the “Extract using XPATH” field to fine tune what you need from the HTML Page. For example, if I want all the links in the page I can simply use “//a” to grab all links. If I want all the images in the html I can do “//img”. Read more on XPATH. You can also find XPATH statements using firebug/developer tools to target data that you want in a HTML page.