Why can't I upgrade the iOS on my iPhone 6?

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.

Update to what version? You can only update the iPhone 6 to iOS 12.x.

What is preventing you from signing in to iCloud? What happens when you try?