You can associate a callback with an authentication system using either the Data Administration Console or the Data Administration tool. Both allow you to specify the name of an ABL authentication callback that is in the PROPATH. (You can also specify a fully-qualified pathname, but that would limit the portability of the configuration.)

In the Data Administration Console, navigate to the Security Summary panel of a connected database and click Edit authentication systems.

In the Data Administration tool, choose Admin > Security > Domain Maintenance > Authentication Systems from the main menu bar after connecting to a database.

See the online help in each tool for more information.