1. Charge the Battery
2. disconnect negative battery terminal and connect muti-meter between negative post of battery and negative battery terminal
3. If there is a drain on the battery big enough to make it go dead there should be more than .4 milli amps registering on the meter.
4. if there is unplug one fuse at a time in the fuse panel until you find the one that makes the meter fall to the normal range. (trouble shoot that circuit to find problem)
5. if no fuse affects the meter reading disconnect the two wire plug from the alternator if that makes the reading fall to normal the alternator is a fault.
Hope this helps