Iam using iPhone 6 Plus i need to update my iOS into 15 because apps are not able to installing so can you pls help me how to update iOS 15 or 16 in my phone

iPhone 6 Plus, iOS 12

iOS 12.5.7 is the latest iOS security update for iPhone 6 Plus.

Go to Settings -> General -> Software Update -> Download and Install (if you haven't already done that).

iPhone 6 Plus can’t be update to a higher iOS (13 and later). 

If you have an outdated iPhone that cannot be updated to iOS 13 or later, many apps will not be able to download.

Outdated iPhone no longer meets the requirements for many apps.

Most apps require iOS 13.4 or later.                                

Considering a newer type of iPhone?

Read this before you buy a newer type iPhone.