How do I let my users create organic groups? [n00b apologies] I have installed Organic Groups but am apparently too dumb to understand it.

How do I let me users create and administer their own groups? What do I need to do on the admin pages, and how do I add something on the main page to let them administer &amp; join groups.

Sorry if this sounds dumb



Update: if they can't, and I have to - how do I add a "groups" item to the man menu and a sub-menu for each group?
see documentation for Drupal 6 http://drupal.org/documentation/modules/og or Drupal 7 http://drupal.org/node/1114852.