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When you unzip the download, you get an application named TorBrowser_en-US, so I renamed it to TorNetwork.
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Important: do not copy the port number you see here. It differs on every Mac and even may differ every time you reconnect to the Tor Network.
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The next step is to choose 'System Preferences' from the Apple-manu and choose 'Network'
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Choose your active network connection (1) and click 'Advanced...' (2)
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When you have that, choose the 'Proxies'-tab (1), check the 'SOCKS Proxy' (2) from the list and enter the IP-address and port number (3) which you noted earlier from the network settings from the Tor Browser.
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Click 'OK' and then click 'Apply'.
Now all your Mac's internet traffic is routed via the Tor Network - you can use any browser, any torrent-client, it does not matter.
It is of course all a bit slower than normal, but hey, with today's (semi)-governmental internet-censorships and other restrictions, which are really big nuisances, one is likely to accept some smaller nuisances like a slower connection.
If you are done and want your regular internet connection back, simply quit Vidalia and uncheck the 'SOCKS Proxy' in the 'Network'-system preference. And when you want to reconnect, start again at step 2.