Please upload your file to cloud storage (i.e. Google Drive, OneDrive...etc.) to share it.
Go to Private Space (i.e. Meeting Room or Classroom).
Open "Quick Access" > Tap "Invite" to share it with friends.
Open "Main Menu"> Click "File" or "Browser"> Open your presentation and click "Share Screen" in the upper right corner. Make sure your file has already been saved to the cloud and an invitation message is accepted from your friend as well.
*Note: You are able to share the screen for 20 mins.