Wordpress eBay plugin, ads are displayed based on the post tags or custom tags you assign to a post in your WordPress blog.
You will need to register at the eBay Partner Network eBayPartnerNetwork.com and create a campaign id. A Campaign ID is issued to you by eBay Partner Network. To find your Campaign ID, log into the eBay Partner Network and click "Campaigns" in the top menu bar. You will be given a list of your current campaigs and their IDs, simply copy and paste the one you want to use or create a new one. If you need more help, go here: http://www.wptagads.com/how-to-create-an-ebay-campaign-id/
Go here: [wptagads.com] http://www.wptagads.com/getting-started-with-wp-tag-ads-2-0/