I launched a cluster, now what do I do?

You can view the official Elasticsearch docs here, though it might be easier to start with the README of the client library of your choice. There's one for just about every language listed here. You can also use one of the native Java Client classes. The basic process for getting started is creating an index with desired settings/mappings, indexing documents, and writing application code to search. 

If you're interested in more specific examples, take a look at these articles from our blog about getting started, the ELK stack, and addressing the 'gazillion shard problem'. If you have any questions, contact support and we'll be happy to assist and offer advice: https://qbox.io/support