How to turn on 3G on iPhone5?

Please help me…

Settings > Cellular > Enable 3G

(assuming on iOS 7)

If your on ios 7:
Settings
Mobile (under Airplane Mode)
Enable 3G/LTE
Switch to on position

If your on ios 6:

setting
general
cellular
Turn on the 3G by moving the slider to on

If this is already on, it might not be getting 3G because there isn't a good enough internet connection in your area. Try going into a town/city then you'll get 3G

If you know there's 3G in your area, do a reset:

Hold power and home
Phone switches off (keep holding them)
Then release when you see the apple logo
Phone then starts up!

If you don't know what ios, your running:

Goto
Settings
General
About
Then find version then it will say: ios 6.x.x or ios 7.x.x

And X is any number because they are lots of versions made and the first number is only important