All users in SalesScreen require a user license. To add a user license, you need Account Owner access privileges.
If you don't have the necessary access levels, you will be presented with a list of Account Owners when you try to add a user to SalesScreen and you don't have enough available licenses in your account.
Adding more licenses to your subscription
Go to the Subscription page
You are presented with a page that lists your subscription details, your number of active users, and Account Owners in your SalesScreen instance. Click the Add Licenses button in the top right
The current subscription(s) for your account will show up. Press Add Licenses for the subscription you want to add more licenses to.
You will get a summary of the cost of the licenses you're adding, and the total amount for your subscription. Press Confirm, and the transaction will go through.
Changes in future billing will happen according to the terms and conditions of your subscription.