Update for my iPhone iOS 15

Assuming 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. 

Hey there,

did you follow the steps in this article ☞ Update your iPhone, iPad, or iPod touch - Apple Support

do you have any trouble with the update?