Add the Peacock channel app to your Roku account from the Roku channel store. It should download to your Roku automatically.
Load the app and log into it, using your Peacock login credentials. If you see a screen saying something like "Log in with your Roku email" this is just an offer to save you typing it in yourself. If your Peacock subscription uses a different email address, don't click "Continue" but proceed to manually enter the correct email.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X