This guide will help you configure the Wiki plugin correctly, this includes:
You have to select a namespace for the content of this plugin. This namespace may NOT be in use currently, if it's you registration will fail. Pages created with this plugin will be publicly available under the namespace you select. If you choose the namespace: MyNameSpace, and create a page named: MyFirstPlainHTMLPage, you may access the page publicly at this address: CMS3URLMyNameSpace/MyFirstPlainHTMLPage. Namespace:
If you have pressed the apply button during each step, you should be done with the configuration of this plugin.