How do I delete all messages in my in box all at once rather than 1 at a time

My inbox is full of messages brought over from Outlook 2016 and I want to remove them all at once rather than one at a time.  How do I do this?

Thank you.

  1.  In the message list, highlight the first message
  2.  Scroll to the last message in the list
  3.  While pressing the shift key, highlight the last message.  This should highlight all messages.
  4.  Press the delete key or click on the delete toolbar icon

Thanks again.  I thought there must be a way to to this.