You can check if battery is bad, jump start with cables from your car battery.. if bike starts nicely your battery is dead. Some batterys last only year (or less) , when you buy new battery make sure it's meant to MOTORCYCLE not to lawnmover. Motorcycle batterys are made tolerate more vibrations, if your ironhead don't vibrate you don't need battery :-)
If battery is drained after bike is running check charging as IronMick wrote.