Can’t find my API Key

I installed a wordpress blog using fantastico and didn’t recieve an email with an API Key (or if I did DH has kindly deleted it). I can’t seem to find it. If I log into my wp_admin area it is not there.
Do I need to register with wordpress.com? Some of the answers to previous posts on this topic have suggested that? Won’t this just set up a completely new account/blog unconnected to what I have already set up?
If anyone can help with this with very simple instructions I would be really really appreciative.

Thanks,

Sara