There are multiple ways to entitle your users to certain Bentley applications.
Each level is over-ridden by the subsequent level. For example, the default access for MicroStation for United States is set to denied, but an IMS user is set to allowed. The IMS user will be allowed to use that application. All of these may be managed by Administrators and Co-Administrators from Entitlement Management.
A guide of best practices for managing entitlements is located here: Access Controls Best Practices