Subscriptions exist independently of brands. From the Subscriptions and Billing page, you can unassign a subscription from one brand that you may no longer want to support and assign it to a new brand.
Start by visiting the Subscriptions and Billing page here: https://www.presshook.com/subscriptions/
NOTE: Unassigned subscriptions are still brands that are actively billed. Unassigning a subscription from a brand does NOT cancel the subscription.
From the unassigned brands section, select "Assign Subscription" from the brands submenu shown below.
Afterward, you'll need to select a brand to assign it to.
After you've selected a brand, that brand will now be associated with that active subscription. You'll be able to modify it and pitch media on it's behalf.