Aditional content areas

I am a (exited) newbie to MODX and started on a very simple site.
I am interested in making an aditional content area for posting update about the project the site is about. It is the box on the right side of the page here: http://gribskovkunsthus.dk/DetSker.html

How do I make the content of the page editable by content editors?
I believe this is a normal newbie question. Is there simple turtorial that demonstrate this?

Thanks a lot.

You need a TV (otherwise known as Template Variable). You can setup as many editable content areas as you may need. Read more about this great feature here:
http://www.modxcms.com/template-variables.html

and here:
http://modxcms.com/forums/index.php/topic,9989.msg72198.html#msg72198