Camtasia Tutorials are available from Techsmith at the Camtasia studio website. They are excellent for learning how to use the software from a technical perspective. You can use them to weigh up wherever or not you will get the use out of Camtasia that warrants the investment.
You may also find information from other users invaluable as the practice is often different to the theory. You can use Camtasia to record PowerPoint Presentations. Here is my experience in converting PowerPoint to video.
If you are not used to making audios of your speaking voice it takes a bit of getting used to. If you unsure at first you can always put music to the slides. You need to sound confident if you are going to narrate yourself using a microphone. Firstly you need to prepare your slides, you can use animations as well as text as I expect you know. You can get free graphics at IconFinder to help pimp it up a bit. Timing is everything when reading along with the slides but there is a rehearsal button so you can have unlimited rehearsals that will make it easy to produce a video that looks professional. If you can impersonate your personality into the words so much the better. You need to have a connection between what is being said and what is on view. The main ingredient to the voice over aspect of the video is to have a natural conversation and not sound like a hard sell so speak like you normally speak, assuming you are not a manic depressive!
When you have your Power Point presentation slides finished and have practiced reading your script, you now need to open up Camtasia. If you do not have it I can tell you it costs around $ 300 but there is a 30-day free trial available. It is amazing how easy it is to let 30 days slip by without really getting to grips with the software. During that month try to get lots of use so that you have an idea if you will use the software in the long term, Camtasia also has good technical tutorials for you to watch. There are Camtasia Tutorials that are available for you to watch before you sign up for your trial. It is a good plan to look at the free videos before signing up so you can get right to creating your video once you get the free trial.
Actually you can record the whole thing in PowerPoint if you have PowerPoint 2010 but it is better to do your practice runs then record your slides with no soundtrack and import them into Camtasia. Once there you can record your soundtrack or add your music or both depending on your skill level. Music instead of narration can work if your slides are good enough. Many people do not like the sound of their own voice so prefer a bit of cool jazz instead. However if you can impersonate your own personality and encourage empathy with your message you are a good way to having a successful product.