Select Cmd-k or press the "Connect" button to bring up the connection sheet (It automatically comes up when a new window is opened). Fill in the connection information. Press the "Connect button". The status at the top of the page will let you know if the database connection is successful and ready to handle queries.

In addition to manually entering the connection information, PostMan Query also supports saving connection information (via preferences). Once the connection information is saved in preferences, it is available from the drop-down menu in the connection panel. Selecting one of the saved connections automatically fills out the connection fields. Press the Connect button to finish the connection. The status at the top of the page will let you know if the database connection is successful.