At the start of your turn, declare how many Steam Points your Steam Tank is generating – this can be any number between 0 and 5. After you have generated your Steam Points (if any), roll an artillery dice to see if the Steam Tank's boiler holds out. If the result is greater than the Steam Tank's current number of Wounds, or if you roll a misfire, roll a D3 and then, for each Steam Point the Steam Tank currently has, add 1 to the result and consult the Steam Boiler Mishap table.
You can expend Steam Points in three ways: through the Steam Engine, or Steam Weapons. You can expend up to 3 Steam Points in each of these categories, as long as you have enough Steam Points remaining. Any Steam Points left unused at the end of your turn are lost.