Good news for you: there is no need to create an Elasticsearch index before using it in WPSOLR.
Because WPSOLR will create one for you, automatically. Even better, it will also configure it during the nex step.
But I prefer to create it by myself!
WPSOLR creates an index with the default parameters proposed by your Elasticsearch server.
If you want to use your own parameters, like the number of shards, you can create the index manually.
WPSOLR will then apply it’s mappings to your index, but you can also update them if you need to.
Errors and warnings during the index creation
No processor type exists with name [attachment]
You need to install the ingest attachments plugin on your Elasticsearchs server, to be able to index and search attachment files (like pdfs).
MapperParsingException: No handler for type [attachment] declared on field [file]
MapperParsingException[No handler for type [keyword] declared on field [id]]
Your are running an Elasticsearch 2.x
You need to run Elasticsearch 5.x to get the “keyword” type.