Site wide announcement banner I am looking for a plug-in that would allow me to add a site wide announcement banner to the top of a page. Much like the one in the image below:

 

I'm new to Craft and have gotten my site up and running but can't seem to figure out a simple way to do this.
You don't need a plugin for this task. You are free to do whatever you like in your templates. There is a template folder in your Craft directory where your html/twig files live and you are free to create the html you like.

So if you want to have a site wide banner, just include the required html in your layout template and that's basically it. 

Craft is not made for non-developers so if you are going to create a site with craft you should have basic knowledge in html/css to write your layout at least.

I suggest you to read the docs or some other tutorials