Ideally a multi stage automatic charger is the best route, but a decent car charger is OK a long as you dont leave it on for extended periods of time, and check the electrolyte level to ensure the liquid is above the plates (unless you have a "sealed for life" battery)
With a car charger, give a full charge for 24 hours then take off charge and check each month with a multimeter.
Keep the battery in a frost free location but well ventilated.