For role-based access control (RBAC) to work properly, you must enable it for your API using either the Dashboard or the Management API. The Authorization Core functionality is different from the Authorization Extension. For a comparison, read Authorization Core vs. Authorization Extension.
There are two ways to assign a permission to a user. You can choose a user from the Users list and then assign a permission or you can go to the User Details (user profile) page for an individual user and choose a permission to assign in the Permissions tab.
Make a POST call to the Assign User Permissions endpoint. Be sure to replace USER_ID, MGMT_API_ACCESS_TOKEN, API_IDENTIFIER, and PERMISSION_NAME placeholder values with your user ID, Management API , API identifier(s), and permission name(s), respectively.