Backup iPhone/iPad/iPod touch firstly.
Make sure you have a backup on computer, and iPhone/iPad/iPod be fully charged.
3 Steps to Reach iOS 8.2
Step 1. Type: Settings > General > Software Update, and Find iOS 8.2 Update
Step 2. Download and Install > type your passcode > agree “Terms and Conditions”
Step 3. Install iOS 8.2 after downloading
Notice: The whole process may take you half an hour. Be patient !
The steps above is available to any iPhone 4/4S/5/5S/6/6 (Plus), iPad, iPod, iPod touch. Welcome comment below !
iOS 8.1.3 vs iOS 8.2