How to Turn Your iPhone On and Off
The Sleep/Wake button is what turns your iPhone on and off. Apple has taken the time to partially charge your iPhone at the factory, so when you buy it, you’ll get some measure of instant gratification when you turn it on for the first time.
After taking your iPhone out of the box, press and hold the Sleep/Wake button at the top-right edge. The famous Apple logo should show up on your screen, followed a few seconds later by a stunning image of Earth.
To turn the device off, press and hold the Sleep/Wake button again until a red arrow appears at the top of the screen. Then drag the arrow to the right with your finger. Tap Cancel if you want to change your mind.
While you can keep your iPhone turned on all the time, many people choose to turn off their iPhones off during times of indisposition, such as when they are sleeping, at work, out to dinner with friends, or in a movie theater. This saves your battery for the times when you do want to use your iPhone (and saves you from rude glances from other movie-going patrons if your phone starts to ring during a movie's climax).