Milestones are collections of Epics, which in turn are collections of Stories. You can access the Milestones Page by selecting "Milestones" in the left-hand Clubhouse sidebar menu. Milestones are the highest level of organizational hierarchy in Clubhouse.
Want to see Milestones in action? Explore our Sample Workspace, which contains pre-filled information that will allow you to see how it all works together. Access it by clicking on your User Icon on top right > Help / Feedback > Sample Workspace.