How to configure this module without routing and config form

The 8.0.x-dev branch of this module (including 8.0.0-alpha1) uses Search API's configuration forms...

1. To add an Elasticsearch server, go to /admin/config/search/search-api, click the Add server button, set Backend to ElasticSearch, and fill in the Configure ElasticSearch backend section of the form.
2. To add an Elasticsearch index, go to /admin/config/search/search-api, click the "Add index" button, and set Server to a server whose Backend is set to ElasticSearch, fill in the rest of the index information, and click Save and add fields. In the next step, click Add next to each field you want to index (you will configure the fields in the next step), then click Done. Configure the fields, then click Save changes. Click Processors at the top to modify processors.
3. To see a list of Elasticsearch servers and indexes, go to /admin/config/search/search-api
4. To edit an Elasticsearch server and/or index, go to /admin/config/search/search-api and click the Edit button next to the server or index that you want to change. When editing an index, use the Edit, Fields, and Processors tabs at the top to change those things.
5. To delete an Elasticsearch server or index, go to /admin/config/search/search-api and click the Delete button next to the server or index that you want to delete.