Site: www.woosa.it So I am trying to add some layers on top

Site: http://www.woosa.it

So I am trying to add some layers on top of other layers, and I am having trouble figuring out how to work the z-index settings.

I have a Cimy image rotator plugin for my header. I need to add a logo and a button overtop of that. Just below the slider, I would like to add a banner and background that overlaps slightly. The background will be light-grey/white. I plan to add many different elements on-top of this grey background, so I would like to know how to identify each element with a Z-Index.

All of my code goes into a widget, or in the custom includes for style sheets. Ultimately, I would like to include the z-index in the widget elements rather than separately in the custom includes where I might lose track of it.

For example, currently my code for my logo is
<p><img src="http://woosa.it/wp-content/uploads/2015/01/Header-Overlay1.png" alt="" width="65%" height="10%" style="float: right; clear: none; margin-right: 40px; margin-top: -54%;" /></p>

This logo is stuck under the slider and can only be seen during transitions. I tried adding a z-index to the code but I wasn't sure how or where to place it. I tried adding it like this:

<p><img src="http://woosa.it/wp-content/uploads/2015/01/Header-Overlay1.png" alt="" width="65%" height="10%" style="float: right; clear: none; margin-right: 40px; margin-top: -54%; z-index: 9000;" /></p>

It didn't work, so I'm wondering if there is another way to include it in that snippet or is my only option to add the z-index through the custom includes?