Ok, sounds like the template folder did not get copied to your theme. This can happen in some environments (eg if you have security plugin or server rules that prevent writing to the active theme directory).
In the plugin’s root directory you will find a folder called /template. You can override that folder and any of the files within, by copying them into your active theme and renaming the folder to /yourtheme/wp_knowledgebase. WP Knowledgebase plugin will automatically load any template files you have in that folder in your theme, and use them instead of its default template files. If no such folder or files exist in your theme, it will use the ones from the plugin.
