How to factory unlock a iphone xs

I do not know what you mean by 'factory unlock'

Do you mean you want to reset/restore to factory settings?

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

device activation locked?

Turn off Activation Lock - Apple Support

remove carrier lock?

How to unlock your iPhone for use with a different carrier - Apple Support

ok, click on the link in my post (blue text) and the support article should direct you with the procedure to factory reset