Step 1: Log into Drupal 8
Step 2: Click Reports at the top
Step 3: Click Available updates
Step 4: Click the Settings tab
Step 5: Check the box to Check for updates of uninstalled modules and themes
Step 6: Add any email addresses you want to notify (or remove all email addresses to send no emails)
Step 7: You can also check available updates in the Reports section
Step 8: Click Save configuration