Extra field in article

Hi,

i need some help for creating an extra field...

1. I've created the override of com_content so i got "template/html/com_content/article with 3 files. default.xml, default.php and default_links.php
2. default.php needs to be modified where i can read my parameter: (http://t3-framework.org/documentation/extend-com-content.html#add-extra-fields)
2.1 $attribs = new JRegistry($this->item->attribs);
2.2 logic

The question is now, where i should put my custom fieldset with the field? I mean i need to register this field anywhere....

If i put it to default.xml (template/html/com_content/article/default.xml) i can't see anything in my article. No extra tab.








Thanks,
Eugen