The content for your alert is edited in the section (Content > Sections) Subsite - Alert Popup. 

You can add any kind of text, links, images or buttons in the content field. 

You can swap out the alert's content anytime you need to!

In the section Subsite - Alert Popup, a "Hide Popup" checkbox has been added in. Simply check the box to hide the alert from your site, and uncheck the box to put it back on your site!