<?php
$config_storage = \Drupal::service('config.storage');
$config_path = drupal_get_path('module', 'feature_name') . '/config/install';
$source = new FileStorage($config_path);
// Wrap the next line in a foreach loop parsing your configuration files
// located in $config_storage, and importing it.
// file_name and config_name are identicals. Do not add the .yml part of the
// filename.
$config_storage->write('file_name', $source->read('config_name'));