It sounds like you need some fields that match each other and are common to both reports (or, to be more generic, data sources).
If you have those then it's a question of which join type you need to use to get the result you want. Different joins allow you achieve different results.
I'm not sure about your need to connect to 2 table extracts. In principle I think it should be possible unless there is some constraint in security policy perhaps?
You would have 2 queries available, just like 2 reports can be available, and you would join them in much the same way.
It's difficult to be more specific without seeing the problem but I appreciate that you are are probably not able to make screen copies available to help with visualizing the problem.