There are several ways to go about adding additional licenses to your plan. Your Account Manager is the best person to speak to in regards to purchasing additional licenses or products.
Ways to contact your Account Manager
In-App, there's a quick and easy way to get in touch with your Account Manager
To do this, you'll want to go to "User Management" from the Admin Center
From here, you'll see a button with a CTA on it to "Buy Licenses"
If you press "Buy Licenses" you'll see the following popup which allows you to schedule time with your Account Manager or launch a call in real-time if they're available.
If you try to activate more licenses than you've purchased that you'll see a similar popup prompting you to connect with your Account Manager to purchase additional licenses.
Another option is to just reach out to your Account Manager directly via their email and they'd be more than happy to help you out!