How to upgrade my iPhone iOS 14.1

To update to the most recent, compatible version of iOS, please 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. 

See this article.

Update your iPhone or iPad - Apple Support

Of course, if your iPhone is old, it cannot run recent iOS versions.