So you're asking yourself how to use eureka!

Actually it's quite simple and straightforward:

1. Download the source code and unzip it to a directory reachable by your webserver. I suggest https://svn.mydomain.com/eureka for eureka and https://svn.mydomain.com/repository for browsing through your repository (in case you wanna do that and have the neccessary plugins installed)
2. This is tremendous important: Make sure, eureka! cannot be reached by every of your web site visitors. Otherwise you may encounter strong headaches :) Best thing is: use http authentication (see below)
3. Make sure, your web server may access all neccessary directories. Maybe you need to adjust your php's basedir_restriction.
4. Open index.php and set all parameters in the configuration part (such as svn url, repository name etc.)
5. Create a file eureka_exclude.txt, open it and add all your permanent files' names (that is: those that should not be overwritten in docroot, e.g. configuration files).

Example:

config/config.php
web/js/*test.js

6. After you checked in a change into your svn, simply start eureka! in your browser (if you followed my suggestion, open https://svn.mydomain.com/eureka) and click eureka!. That's it. Check out the log on the page to find errors in your configuration.

Can you give me an example how to secure eureka!-dir?

Sure. Easiest way to do it is to use your web server's HTTP authentication.

If you use Apache, you should modify your Apache configuration similar to the following:

<Location "/eureka">
 AuthType Basic
 AuthName "eureka!"
 AuthUserFile /etc/apache2/eureka_passwd
 <IfModule mod_php5.c>
   php_admin_flag engine on
   php_admin_flag safe_mode off
   php_admin_value open_basedir "/etc/apache2/htdocs/:/tmp/svn_temporary_checkout"
 </IfModule>
</Location>