Help adding thumbnail images to pages

Hello,

I purchasde a theme called Centita and love it. Although I am trying to find a way to add the thumbnail that I upload using the custom-fields option.

I have separate images I want to appear directly under the header of my site. I was told I need to add a static image block above the page code. I really only partially know what they were talking about.

So..How do I do this???

My website is: http://www.modernedge.net

On the main page you will see an image slider. I want the stationary image to appear in teh same position as that on every other subsequent page.