Please read the chapter about installation of a wiki in the DokuWiki manual.
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If you are looking to create multiple Wiki's, you can create a DokuWiki farm. This is similar to the idea of multi-sites. Instructions on how to do this manually are provided in the Farm page.
In a nutshell, you can install as many DokuWiki instances as you like by simply using a different directory for each withiin the web root, or you can install one instance and use a farm.