I’m trying to create a silent subliminal that can be attached to any music. I’m using windows 10. I’ve gotten as far as importing the message/ affirmations in an mp3 file. can someone please help I don’t know where to go from here? I’m not very tech-savvy but am trying… simple step-by-step instructions would be greatly appreciated. thank you in advance for your time and assistance.
There’s more than one way to make a “subliminal” file. The easiest way is to reduce the volume of the subliminal by 20dB or more (you can use the Amplify effect with a negative value) and then mix it with “loud” music or white noise. (If you have two or more tracks open in Audacity they will mix when you play or export.) You might have to go as low as -40dB so you can just experiment if the subliminal isn’t completely drowned-out.
With that method it’s possible to subtract-out the music or noise (as long as you keep the original file) and then re-amplify to “expose” the hidden sound/message.
in an mp3 file.
MP3 (and most other lossy compression schemes) compresses the file by throwing-away sounds you can’t hear so you may loose the subliminal information. …In the real world that won’t make any difference if you can’t hear it anyway. 
I’m trying to create a silent subliminal
Some problems with that. Which one? There’s at least three different formulations that I know of and there could be more.
that can be attached to any music.
And that’s the other problem. Subliminals are not Bulldozer/Howitzers. They’re delicate butterfly wings and only work best when the music bed is compatible or at last not actively fighting the message. Relaxation chants and John Philip Sousa, for example, are not a good match.
The formulations are almost all ultra-sonic which means your music system has to be of excellent fidelity. Cheap earbuds and most speaker systems need not apply. It certainly won’t make it through wireless headphones. Wireless has enough trouble passing ordinary music.
There is a third problem whenever anybody gets that far. Subliminals are not college courses. At best they’re one and two word repeated suggestions.
Let us know.
Koz