How do you query data owned by another user?

For example, I have permission to see data owned by another user. My data source is configured for my user account. When I try to "Specify Data Source Settings" in my report, I can't see the other user's tables/views. If I go to "Queries" and "Add Query", I don't see anywhere to simply key-in a SQL statement. Everything works from pick list which only shows items I own. I DO NOT want to use the other user account for my data source.