You can control what users have access to APIs on an Endpoint by Endpoint basis using Roles.
To add a user to a Role, from the Home menu ribbon drop down the API Options item and then User Authentication > API Users
Select the Roles tab. You will see the Roles the user is currently included in.
Click the Add button to open the Select Security Role(s) dialog
From this dialog you can click on an existing Role to add it to the permissions tab. Or you can Click the Add button to add a new Role.