WordPress.org

1. Upload the wp-announcements folder to the plugins directory in your WordPress or WPMU installation.
2. Activate the plugin.
3. To display the marquee in your website: Call the php function wp_announce_marquee('') anywhere in your theme, use the WP-Announce-Marquee Widget or use the Shortcode [wp_announce_marquee] anywhere in your post or page content.
4. For posts checked off as popup announcements: The Popup will popup a new browser window by default unless you specify otherwise, some visitors may receive a popup blocker alert from their browser. Using the Shadowbox JS or ThickBox WordPress plugins are recommended, just upload and activate either plugin and save your popup type.
5. Check marquee or/and popup announcement on any post add/edit page on the bottom left under categories.
6. Manage announcements from the admin page located under "Settings>WP-Announcements".

That's it! A Marquee or Popup will be displayed promoting your announcement.

WP-Announcements Support Forum