1. A sticky shout can be made by first creating a shout. Then you go to either the adminpanel (manage shouts), or to the moderation panel. Click on the green flag behind a shout to make it a sticky.
2. You can disable user registrations by logging in at the adminpanel, then go to "Preferences and Settings". Scrolldown to "Enable user registrations" (under "User system settings"), and untick that box. To prevent guests (unregistered users) from posting, you can tick the box at the "Disable guest posting" option.