As far as I understood you're asking for a application to encrypt your data of the hard disk. You don't course or some kind of training. Here is a software for Linux that you can use to encrypt data.
TrueCrypt Encryption App
Although TrueCrypt has been expired but that's still used by hundreds of thousands of users. TrueCrypt security audit proved that it is still usable. But if you don't to take risk you can try out any other like, VeraCrypt. What you do you follow the article and see how it works and then use VeraCrypt, if you don't like to use TrueCrypt.