Autozone and others can also test your alternator for you.Try AutoZone or OReilly Auto Parts for the book and might have them do a scan on the cars computer for more info from the cars computer.
The belt is on the passenger side of the car, with the engine running it will be the black thing that is driving all of the pully's. Be very careful not to get your hand in there while the engine is running.
I agree with Erik that you have a voltage issue, it may be a bad alternator (which charges the battery and runs the cars electrical power when the engine is running), or possible a worn out belt. With the engine off measure the battery voltage, should be about 12 to 12.5 volts. Now with the engine running measure the alternator output, should be between 13.2 to 14.5. If the voltage is not up in this range replace the alternator.
If neither one is the problem then I would check for a problem in the steering column, it may be that the steering column ground is bad or a power wire is bad, with out checking the car out it is hard to say.
If you are not very good at tracing electrical problems out you may find it easier to have a good mechanic check this out for you.