When you register for an E-junkie account, you will have your own login on the E-junkie site with your own Seller Admin where you add and configure products to sell. Just click the Sellers tab above if that's not highlighted already after you're logged in, then click Seller Admin.
Once you set up your products in your E-junkie Seller Admin, we provide you with ready-made HTML codes for your cart buttons, so you would simply copy the codes from us and paste them into the HTML source of your own Web site pages, wherever you want our buttons to appear among your own layout, text and images. If your product will issue a file download, you would simply upload that file to our server when adding the product in your E-junkie Seller Admin.
Our Getting Started help page is a good place to begin setting up E-junkie on your site:
http://www.e-junkie.com/ej/help.sell.htm