Researching silent subliminal recording systems, I came across a suggestion that I could use Audacity. Which I downloaded for free (thank you very much) Could someone please direct me from here on, as to whether I can do Silent subliminal recording, and if they would work on Audacity… and if so HOW to 
Michaela,
Audacity is not a silent subliminal recording system. However Audacity, as an outstanding audio editor, could be used as a tool to mix any such sounds that might be recordable on an audio CD. Your job then, is to find out exactly how this is done, then use Audacity to produce your results.
I hope this helps.
There was a recent discussion about this: https://forum.audacityteam.org/t/subliminal-messages/10509/1