Adding pictures to posts

Hey guys, I’ve been trying to figure this out for a while. Almost every magazine plugin that I install for my video web site has a top sidebar or a place where I can view a gallery of images that every image leads to a post.

This is my website, and as you can see the top bar has no images on it. This is how it is supposed to look. (You can see an image of a windmill, some kind of flower, and a website up there.)

I would like to know how to add an image to my post so that it will show up there. (I know how to attach an image/video to the post itself, but I don’t want the image to be IN the post, I just want the top bar to show an image that LEADS to the post.)