eNotes does offer complete texts of many works in the public domanin, but unfortunately not this one. When you click "Study Guide," you will see a tab titled "eTexts" if there is an electronic text for a work on our site.
In order to find stories themselves, you can conduct an Internet search under the search engine of your choice. (I tend to use either Google or Google Scholar.)
Outside of that, in order to find the story (given it opens as a document and cannot be linked), you need to go to Google and type in Charles by Shirley Jackson into the search bar. You will select the first link.) By doing this, many of Jackson's stories can be found easily on-line. The first link below will take you to the eNotes site on Charles. Here you can find all you will need to know about the story (characters, themes, overviews, setting, and a character analysis).
Additionally, Project Gutenberg has almost every work available free of charge that is in public domain. Be sure to check them out. http://www.gutenberg.org/