Summarize this article:

Steaming doesn't cook the top sides of the eggs as quickly as contact with the pan, so you'll need to allow a little extra cooking time. The eggs are cooked to over easy when they're covered with a thin white film but the yolks are still liquid.  Be sure to reduce the heat to low hear to prevent the bottoms of the eggs from over-cooking from the heat of the pan. If, after a minute or two, the eggs don't seem cooked, try turning off the heat and letting the residual heat warm them a little longer.

Summary:
Steam over low heat for a minute or two.