Librato was built as a generic monitoring service so there are many ways to collect metrics.
The fastest and easiest way to get started is to use one of the Librato Integrations. These solutions offer the quickest path to get from configuration to curated dashboards for things like servers metrics, Docker, Redis, AWS Cloudwatch and many other services.
For more generic metrics you can choose from a large number of collection agents and language bindings. These libraries allow you to instrument your code or use local aggregation agents such as statsd to collect any metric you desire.