It may take up to 4 weeks for Stories to show up after reaching 10k subscribers. Also–if your channel has policy violations such as 2+ strikes, you may not have access to this feature. More info here: https://yt.be/help/QQyp
It's rolling out slowly while we continue to test it out and gather feedback! In the meantime, here’s a bit more info: https://yt.be/help/QQyp If you have further question, reach out to Creator Support team. Here's how: https://yt.be/help/partners