How do I update my iPhone to download apps ?

Nightlight74 wrote:

I need my phone updated

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. 

Your tag line says that you have an iPhone 6s. You can update that iPhone to the latest release of iOS 15. You cannot update it to iOS 16 or later.