<< 1 - do I need to have a separate ISP account with someone? >>
If you don't have a regular account with a Wi-Fi provider such as BT, you should just be able to buy the time you need at the hotspot - Starbucks, Hotels etc.
<< 2 - is there anything I need to do to enable the wi-fi or does it magically know what its doing? >>
There should be an icon for the Wi-Fi adapter, possibly either in the System Tray or Control Panel. Launching the Wi-Fi monitor will then let it search for any available Hotspots to connect to. Just connect to the network and enter the necessary authentication from the Wi-Fi provider.