External builders are automatically invoked after the DVT builder. For example when requesting to build or rebuild the project, when saving etc. Obviously if the command is empty for a specific phase (full, clean or auto), the builder is not invoked.

You can also explicitly invoke only the external builders from the dedicated button .

The focus must be on some editor in the project or a resource from the project should be selected.

If you have multiple external builders defined for a project, you can select which one will be invoked by clicking on the respective entry in the menu:

NOTE: When invoking only one builder, a Clean Project operation that removes all errors from all external builders is also triggered.