Hi Wysocki,
I'm happy to see someone finally tried it out

Yes, it was indeed a lot of work
That you need to add the plugin to your config is actually written in the instructions given to you when you run the install.bat.
That part is displayed in the cmd after the window openes where you clicked ok to install the plugin btw.
For the webserver, you don't need to add the webserver plugin to your config for this to work at all, it'll configure it's own (hidden) instance of the webserver plugin automatically and you set the settings for it within the configuration dialog in the O-MEGA plugin (after adding it along with all the other required plugins, like SchedulGhost - just watch the EventGhost log after adding the O-MEGA plugin to your config!)
When you also add and configure other instances of the Webserver plugin, make sure they are not set to the same port as configured in the O-MEGA plugin.
Unfortunately there is no user manual yet; I was trying to write one, but after 3 pages plain text there was still little to nothing explained compared to all the features and how to use them, so I kinda gave it up.. (writing manuals is super boring

)
If you follow the link in the first post, you get a short overview of the feature set
The templates and extensions (examples) are basically extending the webinterface with actions or a whole UI to integrate specific devices or programs more easily or from the web UI itself, but it's not required.
When there is no extension for your application available, you can still use the web UI to trigger an event in Eventghost and configure your macro there; just like with any other remote control.
Oh, one more thing; after you have to tool running and can access the web UI, make sure to go to settings -> configuration -> pages and hit the "save" button. That's required to initiate the predefined templates to control your (server) PC. (So, you can directly remote control your mouse/keyboard and windows explorer from the web UI without further configuration)
Btw. Whenever you change any setting in that configuration part within the UI, the system automatically creates a full backup of the webserver files as well as the SchedulGhost configuration file and your EG config tree.
So when you mess up something, you can easily go back to the last state it worked by executing the "RestoreBackup.exe" in the folder of the O-MEGA plugin (usually under c:\programdata\eventghost\plugins)