I finally was able to connect to the database!!!
Followed the first instruction.
Although I got another error:
Error: MetadataRetrievalException: Couldn't retrieve metadata as the request does not have parameter called 'metadata'
This was the what I currently have on my json script:
sql: 'select cast(MAP[\'firstname\'] AS VARCHAR(30)) AS \"first_name\"\n from \"firstdb\".\"table1\"'