You can use Send free download link / code in your E-junkie Dashboard under Manage Buyers in the left-hand sidebar menu to send anyone a code manually anytime.
We're working on a more comprehensive help page for our new WordPress Plugin.
The first time you set up the plugin, it can take several minutes to grab a copy of your product data from our server and generate the storefront in your WP site listing all of your E-junkie products. Make sure you don't have any existing page or subfolder at the Shop URL you enter in your plugin settings.
If nothing shows up after several minutes at the Shop URL you'd entered, it may be conflicting with some other plugin in your WP install -- e.g., the latest case we saw was resolved when the seller removed other plugins for another shopping cart/storefront and a 404 Not Found page customizer (it's not clear which one was the culprit, as they just removed them both).