There are few methods to do so.

• Go to Epics listing view and Select the Linked User Stories option provided next to each Epic. You can view these User stories in 2 modes; minimized and expanded.
  • Minimized view only shows ID and Title.
  • Expanded view show Sprint ID, attachment and so on.
• Edit View of Epic
  • Go to User Stories Tab and view existing association, modify or add new User Stories to Epic.