I think you're not specific enough with your question. I gather that you're looking for a website or app that features scary story, but what I don't know is if you're looking to purchase a scary story and send to your friend or you're simply looking for a reference to a free story site. Another question is, are you looking for a short or regular story site?
For short stories, you can try visiting websites like "FIVE CHAPTERS, STORY, FLASH FICTION ONLINE, etc". All of these sites publish short stories on a daily, weekly and monthly bases. Their archives are jammed with hundreds of stories from different genres, and it's completely free to surf the websites. You can easily find what you're looking for there.
For regular stories on apps, you can try wattpad. This is a user base app with thousands of published stories. You can simply download the app, signin and participate in the story community by publishing stories or reading stories published by other people.
For more references or links to other story websites and apps, try visiting reddit. Reddit has a website and it's also available on app. It's more of a discussion forum and you can find questions and direct answers for your search subject.