How to update my iPhone software?

Assuming you have a compatible device, see: Update your iPhone, iPad, or iPod touch - Apple Support

And: If your iPhone, iPad, or iPod touch won't update - Apple Support

If the above Apple articles do not help, please post back with relevant information. 

jawid227 wrote:

I already used this but not answered my question

Please provide details as to what happens when you attempt to update.