Managing your users is super simple! Go to Settings > Users
Here, you'll see 3 main options:
Edit Roles - allows you to create and define roles for the account, each with their own sets of restrictions and permissions
Delete - allows you to delete a selected reader for user-management
Create - allows you to create, or essentially, add a new user to the account
Fill out all the necessary information and make sure that you select the 'send invitation email' before hitting Save. When done, hit Save or Cancel to start over. The user that's added will then receive an invitation letter to setup their login credentials.