You may browse the instructions, but you will need to register your site before installing.
To install Disqus on DokuWiki:
From your DokuWiki Admin head over to Manage Plugins.
Copy and paste the plugin download link from this page in the field URL.
Head over to Admin > Configuration Settings > Disqus Plugin Settings under Table of Contents. Enter your Shortname.
In your wiki, add ~~DISQUS~~ where you would like Disqus Comments to appear.