To edit the Alert Bar on the top of your site, you will go to Content > Link Lists > Alert Bar

The Name field will be the text that displays as a link, the link field links the user to a page with more information about the announcement, the description field is the actual alert text, and the icon field is the icon that displays next to the text.

A full list of icons is available for your site here: http://mk036.monkpreview.com/_assets/fonts/font-awesome/

To turn the Alert Bar on, the name of Link List must be Alert Bar exactly. To turn the Alert Off, you can add text to the name of the link list, such as the word Off. 

On: Alert Bar

Off: Alert Bar Off