How to update iOS on my iPhone?

Take a look at this link

Update your iPhone or iPad - Apple Support

If you have an IPhone 7 plus, the highest you can update to is iOS 15.8.2.

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.8.2

• If you have an iPhone 8 or X, you can update to 16.7.7

• If you have an iPhone SE (2nd generation or later), or XR through 15, you can update to 17.5.1

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

sanele33 Said:

"How to update iOS on my iPhone?"

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Update Using a Computer:

Have a Computer Handy?: If so, try using a computer to update. Go here: Update your iPhone Using a Computer - User Tip. If any updates are available, they will install, sure enough.