8.0 model A2474

Hi Prin-1,

Welcome to Apple Support Communities. If we understand correctly, you're asking which apps are needed in order to pair an Apple Watch with iPhone. Right?

If so, your iPhone already has the software needed and you don't need to install any apps. Check out the following guidance from Set up and pair your Apple Watch with iPhone - Apple Support.

"Turn on, pair, and set up your Apple Watch

1. Put your Apple Watch on your wrist. Adjust the band or choose a band size so your Apple Watch fits closely but comfortably on your wrist.

For information about changing the band on your Apple Watch, see Remove, change, and fasten Apple Watch bands.

2. To turn on your Apple Watch, press and hold the side button until you see the Apple logo.

3. Bring your iPhone near your Apple Watch, wait for the Apple Watch pairing screen to appear on your iPhone, then tap Continue.

Or open the Apple Watch app on your iPhone, then tap Pair New Watch.

4. Tap Set Up for Myself.

5. When prompted, position your iPhone so that your Apple Watch appears in the viewfinder in the Apple Watch app. This pairs the two devices.

6. Tap Set Up Apple Watch, then follow the instructions on your iPhone and Apple Watch to finish setup."

You might also be referring to which iOS version you need on your iPhone. With watchOS 8, you can pair with iPhone 6s or later with iOS 15 or later. We found that information from Set up and pair your Apple Watch with iPhone - Apple Support. We hope that helps. If that's not quite what you're looking for, let us know exactly what you need to know and we'll look in to it further.

Best wishes.