Thank you for coming to the Community! The ability to assign roles to your additional account users is a feature only available in our new site experience. Your account is still on our old interface and will be upgraded in the future. However, if you would like to expedite the upgrade process I can submit a case to our specialized team that is handling the migration process.
If this is something you are interested in please reach out to us at social_support(at)constantcontact(dot)com with your username and a reference to this post and we can get the gears turning for you.