Please see the draft documentation at Whitelisting or blacklisting forms but note that Kee isn’t really designed to work as a general purpose form filler like this. I think that once you read the new documentation and adjust your configuration (e.g. using www.ebay.com for the domain target) you will probably be able to get it to do what you want but it’s not necessarily going to be perfect for this sort of thing so if you find yourself wanting a wider range of generic form filling features, you might benefit from searching for some additional add-ons that offer more functionality for that sort of thing.
I have created an issue on GitHub to improve the guidance about what to type in the Website box so we can reduce the need for reference to the documentation in future.