I have a peacock subscription purchased through my Apple TV but when I try to open the peacock app it wants my email and password.

Hello Nomad iPro,

You came from this resource: View your purchase history for the App Store, iTunes Store, and other Apple media services - Apple Support

Are you signed in to your Apple ID on the Apple TV? If not, then you'd need to take these steps to sign in and see your subscriptions: Set up your Apple ID on Apple TV - Apple Support

Set up your Apple ID on Apple TV

Your Apple ID is the account you use for just about everything you do on Apple TV, including buying movies or TV shows and subscribing to Apple TV channels in the Apple TV app , and downloading apps from the App Store . You can also use iCloud, which connects you and all of your Apple devices to share photos and more. 

If you already have an Apple ID, enter it when you first set up Apple TV. If you don’t already have an Apple ID, you can create one on the Apple ID webpage. You need only one Apple ID to use Apple TV app, iTunes, iCloud, and Game Center services. For more information, see the Apple ID FAQ webpage.

This may also help out: Subscribe to Apple TV+ or an Apple TV channel in the Apple TV app - Apple Support

In case that doesn't solve this for you, are you in the right user account on the Apple TV? Do you see the Peacock subscription when you look at your previous purchases?

Hoping to hear back, take care.