how do I put iOs 14 on iphone XR?

The iPhone Xr and iOS are compatible and you should be able to install it. See the compatible list near the bottom of iOS 14 - Apple

For instructions see: Update your iPhone, iPad, or iPod touch - Apple Support

Additional information.

Get help with over-the-air iOS updates          

Update – Can’t or can’t restore 

Have you tried using iTunes on a computer or Finder if running Catalina to do the update?

 Update software on iOS devices in iTunes on Mac

If you see an error when you update or restore your iPhone, iPad, or iPod