Tartare,
The distilled water was injected into the combustion chambers to provide a temporary reduction in turbine temperatures and higher thrust. No steam out of the engine, as I remember it from the deck.
The water injection manifold was located very close to the fuel manifold, and wrapped around the engine. The water tank was located just aft of the engine between the aft nozzles. Water was injected at a high rate using a special pump located up in the main wheel bay.
'Wet' operation of the engine was strictly limited, and whether for launch or recovery, was closely monitored.
Hope this helps
Engines