If you are using the plugin along with a theme, which does not claim support for the Affiliate Product Review Plugin, the template tab will appear. If you are using a theme, which supports the plugin (Learn here, how to create a child theme, which supports the plugin), this tab is not displayed, since the themes template files will be in charge.
With this template editor, you can give your reviews a consistent layout. You can use HTML and the plugins shortcodes and group them in the way you like. Important is the tag
#the_content#, which will be replaced by the review text.
You can insert two different templates. The first will be displayed on the review site itself, while the second will replace the review excerpts, for example on the category pages.