If you're running linux..

I'd give it a shot with the old public release of wireshark; http://wiresharkdownloads.riverbed.com/wireshark/src/wireshark-1.6.15.tar.bz2 and then just follow the readme on the github.

If you're running windows, uh.. try something completely different. What's your level of understanding on packet sniffing? Would it be enough to observe the transactions going live on blockchain.info?