[Linda Buquet]

It's easy in WordPress.

In your admin panel hit image.

Enter the url of the image.

Enter a description of the image (the keywords, this will be in add an alt tag to image for SEO>)

Now you will see a string that looks like:
< img src="bannerurl" alt="keyword" />

Highlight the whole string and click Link in your wordpress menu.

When finished you will see
< a href="affiliatelink">< img src="http://bannerurl" alt="keyword" />
(had to add some spaces to get url string to display

Then when you publish or preview you should see the banner and
when you click it should go to the merchant.

Always test your links though to be sure they are tracking.
So after you click, log in to affiliate program and be sure the click showed up.