ODBC Connection to External Data Source

I am looking for procedures on how to connect postgres to an external data source (ODBC to Oracle). I then will query the external data source to write into postgres relations. I can’t find information on how to set up the ODBC connection from postgres to Oracle so I can use SQL in postgres to access data in the Oracle database. I have the Oracle ODBC drivers install and can access them with Excel. I need to also access the database from postgres. Any suggestions on where I can find information on how to make this OBDC connection?

Thanks!

Paul