Have you ever accidentally left your vehicle's interior light on overnight only to be greeted the next morning with a dead battery? If your battery isn't very old, chances are you can resuscitate it with either a jump or your battery charger.
When you use a battery charger, make sure your vehicle is off and the engine has cooled. Make sure your charger is off, and if it requires an outside electrical source, plug it in. After that, attach the positive clamp (red) from the charger to the positive terminal on your vehicle's battery. You can then attach the negative (black) clamp to the negative terminal, but a safer method is to attach it instead to a stable area on the vehicle chassis.
Once the clamps are secure, unless you are in a hurry, turn the charger on to its lowest setting. It will take longer to charge at this setting, but the charge will also likely be more reliable. Depending on the type of charger you have, it should either power off when the battery is fully charged or power off at a set amount of time. If not, turn it to the offsetting. Then remove the clamps in reverse order, negative clamp first, and then the positive. And you should be good to go!