to expand on drinkonlyscotch’s reply…
To get it to work for single pages you must select the “Single Page” radio button on the left then in the “target by URL” box on the right put in your exact page permalink path. So, for example if you installed Atahualpa in the directory “blog” your path would be https://domainname/blog/pagename. Enter “blog/pagename” in the box. Or, if you want the widget to appear on all the pages under that page type “blog/pagename/*”. Permalinks can be ugly so check the format of yours and make it “pretty” if you want it clean.