Hosted on wordpress.com, using Custom fields?

Hello!

I know this has proberbly been asked a milion times before but I’m confused when most of the post seem to be by people who has control over the source code of their blogs. I’ve got a blog that is hosted on wordpress.com and I can’t change any source code (except some for the posts). I tried and add a Custom field in a post, but nothing happend. Nothing was added to my blog post. What am I doing wrong?

Thanks in advance!

/Marlun