[TYPO3] Choose category in my own extension

[Jeppe Donslund]

Hi,


I would like to be able to chose which category of items I wan't to show 
on my page.
I have followed Kaspers Episode 3 video but the category selector box 
does not show up in the backend.

I have extended the tt_content table and applied a set of extended 
fields under Frontend Plugins. But nothing happens.

Is there somewhere some code eg. in ext_tables.php where I can see the 
code for this or where should I look for the error?


Regards
Jeppe Donslund