Nacholibre,
I see others have already posted up to help you, but I too fly with a DX8 G2…You’ll want to plug the interlink cable into the training port side, not the audio port on the back of the radio. Side note, when you go to open realflight, double check the simulation tab in realflight on the main screen, and click on “select controller”. Once there, there should be a grey little arrow / drop down box, and you’ll want to click on the one that says “Spektrum”. Then on the bottom right of that menu, click on calibrate, there will be a prompt to center your sticks, and you have to click again at the bottom right to start calibration. You’ll see a bunch of channels listed (maybe more than the transmitter has, but that’s okay). The extra channels listed can be used with your keyboard, I believe they’re on letters U, I, O, and P? Anyways, Go through all of your channels on your transmitter, and when complete another blue button will light up on the bottom right to finish the process. Once everythings done, you should be ready to fly on realflight. I run realflight 7.5 & 9.5, not sure which version of realflight you have - just thought I’d mention it because 7, 7.5, 9, and 9.5 all calibrate the same way. Happy flying!