I don't have a lot of experience with the CVH engine, but the principle of changing an alternator is pretty universal. Firstly, disconnect your battery's negative lead, this stops any fires or sparks happening when you are fiddleing with the wires. Next disconnect the wires on the back of the alternator, there are normally 2 or 3, one of them being a thick wire, making sure you can remember which goes where. Now find the bolts holding the alternator on. There is usually a long one which the alternator pivots on, and a smaller one which holds it in position, and also allows you to adjust the tension of the drive belt (which drives the alternator from the crankshaft). Once you have taken these out, the alternator should come away. Replace it with the new one, slide the longest bolt in first and tighten it, but leave it loose enough that you can move the alternator up and down on the pivot. Then make sure the belt is around the wheels of the crankshaft and the alternator (and the power steering pump if you have one) - pull the alternator up so the belt is taught and then tighten the second bolt. Then reconnect the wires, and reconnect the negative lead to the battery. Restart the engine and make sure the battery light does not light up on the dashboard.
Incidentally, Halfords often have a Haynes manual for most cars where some home mechanic has gone in and removed the shrink wrap - you can go in and read up on the proceedure :)