I have used this software under Windows OS before and now just trying it out under Puppy Linux: https://www.aescrypt.com/download/
Instead of explaining how here is the video showing it...pretty straight forward: https://files.catbox.moe/zi6j1x.mp4
The basic of it all is that AESCrypt creates a new file of the one being encrypted so you have to delete the original. Then you decrypt it....
Also, to delete the original so it cannot be recovered by recovering software you use:
Shift + Delete
In theory, I have not tested it...