Whew!
What the other guys are saying:
1. Take your volt meter and measure the battery voltage with the engine OFF. Put the + lead on the positive battery terminal and the - lead on the negative terminal. Write down the voltage reading.
2. Start the engine and rev it slightly to get the alternator going (one wire alternators take rpm to start). Let the engine go back to idle. On the back of the alternator is a big terminal lug...the one you touched to make a spark and start this in the first place. Put your + voltmeter lead on this and the - voltmeter lead on the battery negative OR any other ground....like the intake manifold. Read the voltage. Write it down
3. Compare the two readings. When you charge a battery, the charging voltage must be greater than the battery voltage....battery voltage is roughly 12 VDC and the charging voltage out of the alternator should be in the 13.8 to 14 ish range. If the alternator is not putting out more than 12 volts, suspect the alternator.
4. Another way to test the alternator (poor man's test) is to start the engine, rev it to get the alternator started, and then disconnect the battery. If the engine runs on the alternator, then the alternator is putting out some energy...maybe not enough but if the alternator is completely dead, the engine will not run.