The link describes the pass through, but First off you need to use the cables that came with your interlink as well as the interlink itself. Plug in the interlink into your computer. Very necessary because it acts as copy protection for the sim. Then much like a buddy box you use the appropriate cables to connect your trans to the interlink.
You cannot just fly any aircraft in this configuration. You need to select the model you would like to fly and choose to edit it. Under the airplane title you find "radio type". The default setting is "software radio". Click on this setting and choose "pass though". Then choose to save the edit. It will ask you to rename the aircraft. The sim will now use your tx for input to fly that model only or any model you have edited to use pass through.
As for the tx setup you will have to setup a model slot for realflight airplanes and one for helicopters. And each need to be setup just as if for a real life model. How exactly to set it up for your particular tx I don't know, but the above link I provided may help to setup your tx. Good luck!