merged mining not working

[Digicoiner]

I've just started mining bitcoins with guiminer on slush's pool.  I now want to try merged mining with namecoins.  I've installed namecoinj gui, configured the daemon, got a couple of namecoin addresses, and downloaded the blockchain.  I've entered my namecoin address on bitcoincz but no namecoins are being generated.  How do I start generating namecoins.  Do I have to register a namecoin domain?