You can do it! If you don't have anyone to show you, read your manual, and give it a try. If things don't feel right, you panic, or you get tired of it, just push the shift lever back into drive (auto "D" mode), and your car will do what it needs to do with no complaints.
The transmission computer will prevent you from downshifting to early, and will only allow a downshift that will not over rev the motor. In addition, the rev limiter on the motor will prevent you from over revving the motor. The transmission will even automatically select first gear for you when you come to a stop, so you don't accidentally take off from a stop in 4th gear or something. So it is in reality, pretty idiot proof, but there is always one person...(braindead)
However, if you happen to not be paying attention, and have the music up a bit too loud, there is the chance of forgetting that you are in manual mode, and forgetting to look at your tachometer and notice that you have going down the highway at 6300 RPM in 2nd gear for miles.(second)
In closing, it is a whole lot harder to blow up the Auto/Manumatic than a manual transmission with a clutch.
