When you want to assign a license to a user you must buy the subscription first via the Buy subscriptions page.
If the required subscription is not yet available on the user page, you have to buy it first. For previously purchased subscriptions you can increase the number of licenses on the 'Active subscriptions' page.
To buy licenses of a new subscription, you have to navigate to the organizations' overview page. And select 'Buy subscriptions.'
On the 'Buy subscriptions' page, look up the subscription you want to purchase in the 'Available products' section. (Hit enter to view all available subscriptions.)
The 'Available products' contain all products that are on the price plan for your organization.
Select the subscriptions using the “+” icon. It will add the subscription to the 'Shopping cart'.
To change the number of licenses you want to purchase, select the pencil icon. Change the quantity and press Save to finalize.
Review the order and select Buy at the top of the page if you are satisfied with the amount and the billing cycle of choice.