Depends on what sort of underlying file system you want to use on the drive. For Linux filesystems (ext4, btrfs, zfs etc), here's a good start: https://wiki.archlinux.org/title/Dm-crypt
For NTFS, BitLocker is already baked in to Windows.
Bitlocker is only redumentary included in the cheaper Windows "Home" versions
only the "Pro" version actually includes proper Bitlocker tools which is frankly a pretty stupid move
Probably not what you're looking for but Linux Mint has the option to encrypt your drive when you first install it. It's as easy as clicking "yes" and setting a password.
Perhaps you had another partition with an operating system on the same disk, which prevented full disk encryption? If installing on an empty disk, most distros offer full disk encryption by default.
encrypting the drive mainly prevent an eventual thief from getting access to your files, including personal documents and web cookies, since system passwords does absolutely nothing against someone with access to your hard drive, and that includes paswords you may have writtend on a file that you later deleted, where as if you encrypted your drive, there is nothing you have to worry about but to buy another computer if it is stolen
totally valid points, i'm just betting deadbeat eventual thief hasn't got the smart on how to bypass windows passwords. It's a gamble, but i'm willing to look into encryption based just off of that.
Also, it's just a normal security measure. If pirating is illegal in your country it will always be better to encrypt the incriminating material in case of a search warrant.