Not OP, but I'm presuming they mean something like adding a "db_account_password" column to the users table to store the password for that user's database account (i.e. not their password, but the password the app uses to log in to the database as them), so the app can get the credentials to log in to a user's database account before running queries as them.

You'd configure it like a normal webapp with the host, port, username, etc. It wouldn't be something you could just add to the config for an existing app, it would take custom code.