How can i update my software on iphone xr

Assuming you have a compatible device, see: Update your iPhone, iPad, or iPod touch - Apple Support

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

If the above Apple articles do not help, please post back with relevant information. 

Use a computer or the Software Update function in Settings. If you encounter a specific issue, describe it in this thread.

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You can download and install software updates here:

Settings → General → Software Update

Remember to connect to Wi-Fi and a charger. Your iPhone must have more than 50% power to

update without a charger connected. If you are on iOS 14 or older, you must update from a computer.

You can find more useful information here:

Update your iPhone or iPad - Apple Support

If your iPhone or iPad won't update – Apple Support (UK)

If you want to update your iPhone via a PC or Mac, see here:

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

• PC (iTunes): Update your iPhone, iPad, or iPod touch with iTunes - Apple Support