There are many Micro-USB chargers which would work as the power adapter to power a Raspberry Pi with AC power from a wall’s power outler. Your current smartphone, and tablet micro USB charger may work with the Raspberry Pi, but if you want to overclock the Raspberry Pi, or use the Pi for more power intensive tasks like video playback, and gaming, using a Raspberry Pi with 5V/Volts of voltage, and 1A/Amp or higher of current like this Raspberry Pi 5V 1A Micro USB Power Supply would be best for powering your Raspberry Pi. I also recommend picking a power supply with a longer power cable to make plugging in your Pi more convenient when the power outlet, or surge protected power bar is farther away from your Raspberry Pi.
To turn off the Pi, you need to shut it down in Raspbian desktop application launcher on the bottom right of the desktop
You can also type sudo halt in the command line or LXTerminal if you are not in Rasbian. Lastly, you need to remove the power adapter from the Wall’s power outlet to turn off power to the power supply, and the red LED light on the Pi’s circuit board.