Activating Peacock account via Xfinity StreamStore

I'm in the StreamStore and was looking to activate my Peacock subscription, included because of my internet and Xfinity status. Peacock is not listed in my StreamStore subscriptions to 'Activate', but when I go to 'Add & Manage Subscriptions' the Peacock option already says that Peacock Premium (with ads) is already active, and when I go to 'Manage', the only option is to upgrade it, not create an account. How can I create my peacock account so that I can sign in and watch it on my Roku, when the StreamStore says it's already been activated?