Hi Bamberger.
A fellow idiot here. (I recently acquired a netbook, having only ever previously used wired connections, so I've had to find all this stuff out for myself).
Dongles are used to add wifi to devices which don't already have that facility. Netbooks (including Chromebooks) are wi-fi enabled, so you wouldn't need one.
To find wi-fi signal you simply click on the relevant icon a the foot of your screen. It will show all available networks and you simply click on 'Connect' on the one of your choice. Most networks require a password (to stop you 'borrowing' your next door neighbour's internet connection), which you just enter in the box. Some public networks (such as those in McDonald's or Wetherspoon's) require you to open your web browser and try to access any site. If it's the first time you've used their service, you'll be diverted to a registration page; thereafter it's automatic,
The instructions for BT are here:
http://www.btwifi.com/help/login-with-bt/connect-using-your-pc.jsp#win7