Follow these steps, to connect to Postgresql database.
1. Click on Get Data.
2. Go to Database and select Postgresql.
3. Download connector https://github.com/npgsql/Npgsql/releases and install the same.
4. Then Type your server name.
5. Type any Sql statements. (optional)
6. Click Ok.
7. Select required tables and fields residing in Postgresql database for creating your report and visualization.
8. Click Ok.
9. Now the data is retrieved and is ready to create visualizations.
Hope this helps you.