How to Update /Reset your iPhon Firmwaer

To update your iPhone Firmware ,at first you have to know what version of firmware is running on your device.To check your device Firmware version just follow the instructions from your device...................
Tap Setting>General>About  your current ios Firmware version will be shown on your screen.After knowing the current version of your device then check what latest version is available for your device.Then download the particular Firmware version that is suitable for your device.
After completing download check the file format of recently downloaded.If hat is in Zip/Rar format,then just rename it as .ipsw.For example-iPhone6 V2_7.0.2_11A501.zip>iPhone6   

V2_7.0.2_11A501.ipsw.
After this connect your device to iTunes and hold down Shift key (for windows user)  or Option key (for mac user). Now click on Update/reset button and select the ipsw file recently downloaded.Your device should being updated.

Note:For update/reset your device you must have back up your file to iTunes or i Clouds Recommended.Also you must have enough battery life (upper then50%).If you don't have enough, then plug in your device to a power source  (Only for WiFi user).