After unzipping it, you just have to double click on ryzom_updater to update data. You can then launch the game double clicking on Ryzom.
To download or update the client's game data, open Terminal.app, create a Resources directory (if not already there), cd into the app bundle and runrsync:
rsync -rtzv --progress --stats www.ryzom.com::ryzom/data data
rsync -rtzv --progress --stats www.ryzom.com::ryzom/client_default.cfg .
If you already have the ryzom game data on your computer, you may just want to ln -s the data directory into the app bundle.
The client stores config files, logs, screenshots and similar things in "~/Library/Application Support/Ryzom". After running the client the first time, you will find several files like client.cfg and client.log in this directory.
If you want to use your existing character config files from your windows or linux client, move them from the "save" directory in your original Ryzom client directory into ~/Library/Application Support/Ryzom/save/