I'm not a coach, but I stayed at a Holiday Inn Express last night :-)

If you are going to make the investment in a power meter, then you should definitely learn how to use it. The training and racing with a power meter book as suggested above is a great book to get, although parts can get fairly technical.

The main thing the power meter helps with is pacing for intervals, motivation to keep pushing, and quantifying a training load. Too many people say they train with power, but they basically ride around with a power meter on their bike. If there's no structure then you are missing out on a lot of the benefits.

In interval training you are basically shooting for a target average wattage and holding it there for a specified time. My favorite is the 2X20s. 20 minutes on, 5 minutes off, 20 minutes on. It gives a great workout in just about an hour.

At the very start of the interval you'll notice it's pretty easy to go above your target wattage. Let's say you are shooting for a target of 300 watts average. The first couple minutes if you were going by feel you would probably average 340 or more watts, and then barely be able to hold 250 at the end. So the power meter helps to throttle back the effort at the start. Then in the last five minutes of the interval (especially the second one) you can use it for motivation when your legs are on fire and you want to give up. To take advantage of these situations you need to display current watts and average watts only for that interval on the same screen. Most units that can be user configured have this option. That is pretty much the best starting out point. Find out what your max watts that you can hold for 20 minutes and then perform intervals at 87-92% of that number.

Prepare to start crushing souls.