Recording piano on YouTube

[VenalWinfrey]

Bit of a long shot this, but here goes: I am making some YouTube recordings on my digital piano. I have an iMac computer. I have seen some other people's videos, in which they also display a keyboard above their video. As they play notes on their piano, it lights up the keys on the keyboard above, so that people watching can know what notes are being played.

I have asked a couple of the users how they do this, and they have mentioned software like Screenflow/VanBasco.

Does anybody know how I would do this, using my iMac and my digital piano? Is there a free software I can download somewhere, or a resource I can check out to explain to me how to do this? I am not particularly good with technology, and find this all a bit complicated!

Thanks as always for any help.