Here is the Instructions on how to turn ON your iPhone.
It applies to all kind of Iphones wether its Iphone 4, Iphone 4S, Iphone 5, Iphone 5C, Iphone 5S, Iphone 6, Iphone 6 plus
The Sleep/Wake button is what turns your iPhone on
So Press and hold The Sleep/Wake button .
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 Apple Logo.
You may also find Here on – how to turn your iPhone off.