I was having the same issue. Poorly written instructions in the owners manual. First connect your 620 to your computer via the data cable. In the Garmin Express app go to the "Info" area and you should see a new option for "Manage Networks" Click on the link and you should get a pop up window to add or delete wifi connections. Hope this helps. If not, send an email to Garmin and they'll respond within 3 days.
