How can I hook a water heater up to my generator just using 110 can I run an extension cord to just one of the elements for now till I ghet my electris turned on so I can have some warm water

They work fine on 110V, the only difference is how fast the water heats because you are only providing half the wattage. The longer the extension cord the heavier the gauge should be. Use the thickest wire possible to avoid the exCord over-heating.