How do I update the software on my iPhone?

The last update for the iPhone X was iOS 16.7.10.

Tap Settings > General > Software Update to see any available updates for your phone X. If the message says that your software is up to date, you have reached the end of the update road.

The iPhone X cannot run iOS 17 or iOS 18........if that might really be what you are asking.

You cannot update an iPhone X to iOS 17 or 18, if that is what you are asking about.

The iPhone X cannot update past iOS 16, and will tell you that it is up to date if you are already running the highest compatible version of iOS available.

"How do I update the software on my iPhone?: Update my phone"

-------

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

Your tag lines suggests you own an iPhone X. iPhone X can be updated to iOS 16.7.10 and no higher. What are you looking to update to?

The iPhone X can only be updated to IOS 16.7.10 MAX.