Select Users from the top menu, then the Manage Users option.
On this page you will see a statement about how many active subscriptions you have and how many are allocated to a user. By clicking View Active Subscriptions, you will be able to review your valid subscriptions and their expiration dates.
Please note, the active subscription count includes the Administrative user's subscription, so you will only be able to assign/enable users up to the total subscription count - 1 (e.g. if total subscriptions = 5, you can enable 4 users + Administrative user = 5).