Notices is a feature to quickly display messages above other items. You find where to add new ones by clicking the triangular alert button.
The notices window is rather basic: New Notice, to add a new one; Edit Notice, to edit one that already is being displayed; and Remove Notice, to remove a notice that is being displayed.
When you want to add a notice, this is what you will see. First you need to write the notice (the message that you want to display). Secondly you need to decide whether you should display it a certain amount of times or if it should stay active until you delete it (“Infinite?”). Lastly you can set up the font and colour of the notice. (For further notice settings, see Notices tab)
Once you click “Add notice” a red bar will appear at the bottom of your projection (regardless of item showing) with the notice scrolling from right to left (in this example, the Mobile Lyrics URL).