How do you specify in the ADO DataReader destination your db connection to Oracle?

Drop a ADO DataReader destination and add path from your ADO DataSource.
Right click the ADO DataReader Destinaton and in the window that pops-up click on the NEW.. button in the ADO.NET Destination Editor. In the window that pops-up click on the New...button to create a new connection manager and choose .NET Providers for OleDb\Microsoft OLE DB Provider for Oracle. Follow this up by providing the server name and authentication details.

Learn most of regular configuraion in SSIS under two weeks from my illustrated guide:

http://hodentek.blogspot.com/2008/01/about-my-new-book.html