If you are referring to the ones that are often promoted online, by various new-age style "self-help gurus" and the like, my personal advice is - rather don't use them. You never know what is programmed into them and not everyone out there has good intentions. I have read where a lot of these subliminals have been imbedded with nefarious content, like marketing prompts to get unsuspecting people to buy into products, etc. Someone can say to you "this is to help you lose weight / attract wealth / be more confident", and so on. But what proof do you have that this is what the audio or video is actually intended for, when you cannot analyse what is actually being said with your conscious mind. Subliminals are designed to only be heard by the subconscious.
The goal of subliminals is supposed to just be the programming of the subconscious mind with a specific way of thinking or dedication to achieving a goal. But you can do this yourself without having to worry about other people and their potential intentions. It's always better to learn the tools yourself, rather than rely on outisde tools.
Rather practice achieving a Trance state where you can program your own mind according to your individual needs. That way, you are in full control.
Here are some useful links:
https://joyofsatan.org/Trance.html
https://satanisgod.org/Hypnosis.html
Hypnosis may tie into this as well, although not necessarily directly connected with "subliminals". But it's worth studying to understand how the subconscious mind can be affected.
https://ancient-forums.com/threads/the-benefits-of-trance.74755/#post-1098110
Hail Satan!!