I've had to figure this out three times now, so I'm blogging it.

• Install the Lightning add-on for Thunderbird.
• Install the Provider for Microsoft Exchange add-on.
• Click on the Calendar view, and right-click under Home. Choose New Calendar.
• Select "On the network", then Next, and choose Microsoft Exchange.
• This is the unintuitive bit: in Location, put this:

  https://UVIC%5Cnetlink@auto/
  

  Replace "netlink" with your netlink id.
• When asked to log in, use "UVIC\netlink" as your login id.