Workbench moderation and check permissions tab
You're not missing the permissions, just looking in the wrong spot. Log in as an admin user and head over to yoursite.com/admin/people/permissions. This is the main permissions management page which shows all permissions defined by all modules. 

You'll see 'sections' of permissions defined by various modules. There will be 'Node' and 'Workbench Moderation' sections mentioned in the file you read, as well as the relevant permissions.