I want to update the software on my iPhone 6s

To update to the most recent, compatible version of iOS 15.7.3, 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. 

If you have to ask, then your iPhone is probably too old and would not be compatible with the newer software updates.

Click ▶︎ iPhone compatibility with iOS 16 for the complete list.

The time has come:

Shop one-on-one with a Specialist at an Apple Store.

Click ▶︎ Reserve a Shopping Session. 🛒

After purchase, I recommend taking a free workshop to learn all about the new and exciting features of your purchase.

Click ▶︎ Skills: Getting Started with iPhone.