How to enable the Webform module? The tick box is greyed out. What is the "Contribute" module and where can I find it?
You can found it at https://www.drupal.org/project/contribute


  The Contribute module adds a 'Community information' section to
  Drupal's status report (/admin/reports/status) which encourages
  individuals and organizations to join the Drupal community, become
  members of the Drupal Association, and contribute to Drupal projects,
  events, and more.


Maybe you should read this article: The Webform module now depends on the Contribute module