Now you have under app/config/packages/jacopo/laravel-import-export the package configuration files. At this point you need to configure the database access. Open the file app/config/packages/jacopo/laravel-import-export/database.php and update it with the database access information. When done run the following command to initialize ImportExport database.
This command will create a _import_export_temporary_table in the db, you can change the name of the table editing the the key: table_prefix under the file app/config/packages/jacopo/laravel-import-export/baseconf.php.
Congratulations! Now you can view the application at the url: http://url-of-your-baseapp/importer. If needed you can change the base route editing the the key: base_application_route under the file app/config/packages/jacopo/laravel-import-export/baseconf.php.