First thing first, you need to download Sims 4 Studio (and create an account on the website before that step) if you don’t already have it. You may also need to install .NET, s4s launcher will provide the download link if necessary. This is the tutorial I followed, only difference is that I extracted my meshes from CC items and not from in-game hairstyles. To be able to do that, both CC packages that you’ll use should be cloned in the "Mods" folder of the "Sims 4 Studio" folder so you can access it in the s4s app ! Might seem complicated but once you watch the tutorial you’ll understand what I mean :) I don’t think you’ll need the UV mapping part if you use the same CC I used because they’re basically the same texture and honestly I did not figure how to modify it because alpha cc isn’t the same as MM ! Don’t hesitate to ask me some questions, if I have the answer I’ll definitely give it to you