Learning to use Magento have a steep curve (and I really hate walking up hill) but I’ll get there.
To add an image to your home page only…
- Upload the image
- Create a static block that contains the html link to the image
- Duplicate app/design/…/template/page/html/header.phtml
- In Magento admin edit the Home Page (CMS > Manage Pages > Custom Pages)
- Update the Layout Update XML field as per