You can attach a policy in one of two ways:
In the AWS Organizations console, navigate to where you want to assign the policy (the root, an OU, or an account), and then choose Attach Policy.
In the Organizations console, choose the Policies tab and do one of the following: Choose an existing policy, choose Attach Policy from the Actions drop-down list, and then choose the root, OU, or account to which you want to attach the policy.
Choose Create Policy, and then as part of the policy creation workflow, choose the root, OU, or account to which you want to attach the new policy.
For more information, see Managing Policies.