This tutorial will show you how to add and manage Announcements for your site. These are on-site announcements and are not sent out by emails (Newsletter). These show based on the settings you set when creating the Announcement. 

Adding an Announcement

Editing, Deleting, Enabling or Disabling Announcements

Allowing Users to Close Announcements

In order to allow users to close the announcements after they view it, you would need to go in the User Group Settings for each user group. Once in the user group settings screen from that linked tutorial, find the following: