Please I want to upgrade my phone to ios 14.0

To update your iOS, select Settings > General > Software Update. If your iPhone is eligible for an update, you will be prompted to do so. Your iPhone X is capable of iOS 16.3 That is the version you will be offered. You cannot pick a lower version.

Not possible to update to iOS 14 because it is no longer available, but you can update to iOS 15.7.3

Make sure that you have a good Wi-Fi signal and the battery is fully charged.

Tap Settings > General > Software Update to see if the update will appear.

An iPhone X can update to iOS 16 directly.

If you have a different model of iPhone, please provide it.