Updated intro of How to onboard a new data source.
-# How to onboard a new data source? [WIP]
\ No newline at end of file
+# How to onboard a new data source?
+
+In the [metadata-ingestion](https://github.com/linkedin/datahub/tree/master/metadata-ingestion), Data Hub provides various kinds of metadata sources onboarding, including [Hive](https://github.com/linkedin/datahub/tree/master/metadata-ingestion/hive-etl), [Kafka](https://github.com/linkedin/datahub/tree/master/metadata-ingestion/kafka-etl), [LDAP](https://github.com/linkedin/datahub/tree/master/metadata-ingestion/ldap-etl), [mySQL](https://github.com/linkedin/datahub/tree/master/metadata-ingestion/mysql-etl), and generic [RDBMS](https://github.com/linkedin/datahub/tree/master/metadata-ingestion/rdbms-etl) as ETL scripts to feed the metadata to the [GMS](https://github.com/linkedin/datahub/blob/master/docs/what/gms.md).
+
+## 1. Extract
+[WIP]
+
+## 2. Transform
+[WIP]
+
+## 3. Load
+[WIP]
