I am really new at this. How can I add my own photo into the header/banner and eliminate the other rotating images?

You could take out the %image and leave the %logo and use your picture as the logo or you could delete the images used for the rotating banner and replace with just one picture of you. If you are not sure what I mean you need to go through all the various areas in the ATA backend to become familiar with file locations etc. For instance the files for the banner are located in the following folder.

/wp-content/themes/atahualpa/images/header

.

I too am a raw newbie. I am using wordpress through a website I have at network solutions. I want to replace the header image with one of my own but don't know how to access the html code in order to remove unwamted images and add my own. Simply adding the folder to my wordpress web address brings up a page that denies me access. How do I get to the code in order to alter it?

You will need to use ftp to upload and remove image files. If you are not sure how to go about that you should probably check with your host on how to access your site via ftp.