How to update Iphone 4S to IOS 18?

You don't. The iPhone 4s, a phone which originally ran iOS 5.0, cannot be updated to iOS 10, let alone to iOS 18. This obsolete phone doesn't even have a 64-bit processor, let alone the RAM, CPU/GPU power, or Neural Engine needed to run iOS 18.

Apple lists the iPhone 4s as Obsolete.

If you want to run iOS 18, you will need to have an iPhone XR or higher model.

No, I'm sorry. We cannot help.

The 4S is obsolete. Parts and service are no longer available for this product.

You don't.

can you help me my iphone 4s not started