1. Run a 'Wireless Diagnostics'
2. Select a 'Sniffer' in 'Window' menu
3. Choose a channel and channel width, then click 'Start' to begin.
4. Confirm that wifi icon looks like below.
5. Run a wireshark and double click 'Wi-Fi: en0'
6. Wireshark begins to capture packets on the channel you've chosen
