Sure, you need to import it first. I don't know for sure if it came with release 8 or earlier. Open > Administration > Portlet definitions > Import portlet definition > Java-Portlet > select HTML Portlet > Next > ... The URL Portlet was useful for us in the past too.
So I've imported the HTML portlet and added it to a page. I see in the default value it says to click on the Title of the portlet to edit the display but when I do that nothing happens. How do I get to the the screen where I can edit what the portlet is displaying.
In 7.5, you edit the Preferences for the portlet on the module you have created. You just enter the URL where the web page resides. The page can be updated by just changing the file at that URL. I assume 7.1 would use essentially the same process.