The software requires an external VGA adapter attached using USB 2.0 and using a SiS USB VGA chipset. The adapter I am using is made by StarTech.com and is called "USB 2.0 to VGA Display Adaptor USB2VGA2". There are other adapters available and it would be useful if people could let me know (for example, using the forum) if they can report success using any other adapter. The list of known working adapters is below.
The adapter needs to be connected to the tablet, with the tablet operating in USB host mode (a powered hub will be needed). There is information on how to set that up for the N810 in this thread on Internet Tablet Talk.
My configuration uses: the Nokia-supplied USB cable, a USB-A to USB-A gender changer, the standard A-to-B cable for my hub, the powered hub, the USB2VGA2 USB cable. I turn on USB host mode using:
echo host >/sys/devices/platform/musb_hdrc/mode
| StarTech.com | USB 2.0 to VGA Display Adaptor USB2VGA2 | Works |