How can I update my iPhone?

If it is an iPhone SE 1st gen, 6S, 6S Plus, 7 or 7Plus you can update to iOS 15.7.8, see -> iPhone models compatible with iOS 12 -> iOS 16.

iPhone models compatible with iOS 15.5 – Apple Support (UK)

You need about 8 GB device storage and good Service and/or Wi-Fi.

If they are On, turn Off Hotspot & VPN.

Charge the battery > 70%.

Go to Settings -> General -> Software Update -> Download and Install.

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If your iPhone, iPad or iPod touch won’t update

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

You can do the update via PC, see this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

or see:

There is no version 7.5.8

Please tell a valid iOS Version.

ernestames wrote:

but I what update my own my version is 15.7.3

You need one of these iPhones to upgrade to iOS 16.

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support

There is no version 7.5.8

So did you mean you need to update to iOS 15.7.8?

This update is for iPhone 6S,6S+,7,7+ and SE 1st generation.

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support

This info might help you.