Error on WordPress stats using api

I’m trying to use my api on a second weblog for the stats. When I type in the key I get the following message:

Error from last API Key attempt:

The owner of that API Key (Bakkeltje) is not on the access list for this blog. When this blog was registered, USER’s API key was used. To add you to the access list, USER must visit this blog’s stats dashboard page and use the form at the bottom of that page.

I found the form, but don’t really understand how to use it.