How to make a class diagram out of a use case diagram?

I plan to do a system aiming at journalists submitting news stories to editors in view of publishing. This is my use-case diagram:

I struggle somewhat to define the classes based on this diagram.Below is how I've defined key classes so far, using actors and some of the use cases. But I am not sure if this is the right approach.

How do I make a class diagram out of the use case diagram?

Story

Attributes:  storyID  title  content  status (e.g., submitted, approved, rejected, archived)  submissionDateMethods:  getStoryID()  getTitle()  getContent()  getStatus()  setStatus(status)

Journalist

Attributes:  journalistID  name  emailMethods:  submitStory(storyDetails)  getJournalistID()  getName()  getEmail()

Editor

Attributes:  editorID  nameMethods:  reviewStory(story)  approveStory(story)  rejectStory(story)

FileVerification

Attributes:  verificationStatusMethods:  verifyFile(story)

ProcessingCenter

Methods:  processApprovedStory(story)

System Class

Methods:  validateInput(input)  storeData(data)  generateNotification(recipient, message)  sendNotification(notification)