Or if you want use the SVN repository trunk, you can do this from your command line (in the Redmine plugin directory vendor/plugins): svn checkout https://ociotec.com/svn/Software/Web/Redmine/plugins/docs/trunk docs.
Put the plugin into your Redmine plugin directory (vendor/plugins).
Uncompress it (only if you get the tar.gz package): tar -xzvf docs.X.X.X.tar.gz Replace the X.X.X with the version that you have downloaded.
Execute this command from the Redmine plugin directory (vendor/plugins) to migrate the plugin data base tables: rake db:migrate_plugins RAILS_ENV=production Change production with your own environment if needed.