If the battery is dead make sure the water is above the plates. They say you shouldn't fill to the level until the battery is fully charged.
The level to fill to would be just a little below the bottom of the well.
Water should always be added after fully charging the battery. Prior to charging, there should be enough water to cover the plates. If the battery has been discharged (partially or fully), the water level should also be above the plates. Keeping the water at the correct level after a full charge will prevent having to worry about the water level at a different state of charge.
2016 North Point 341RLTS
2012 F-350 Lariat CC SRW