Yes, the 820 is a Nav3 device, so it will use MyDrive Connect.
Let's take this from step 1. First, I can't get the MyDrive web page to add a POI to these Nav3 devices either, even though it appears that it should work. Here's how we've been doing it here.
After connecting your 820, the MyDrive Connect app should appear. Ignore it.
In the lower right corner of your screen (systray), look for your MyDrive icon. Right click it and select "Manage community content"
Your browser will pop up a screen showing the custom POI content on your 820, if there is any already loaded. If not, you'll be adding the first one to the list!
Select the "Add POI" button, browse to the *.ov2 file on your PC, and select "Open" and then "Install" Your 820 should also quickly report "Updating your device", and later "Finished updating your device"
That should do it.