Don't worry, tiz easy. I started with minilinux when I was 11, then I grew into the real deal when I met my mentor. Go to the website, like monkeylinux a known mini distro, flopix etc. Damn I use to know a minlinux distro website with a list of all of them. Yet I know searching on http://www.redhat.com,
their engine... You can find a bunch. So once you find what you want, download the needed files. Then read on the readme or should be on the website for most of them, how to install (like how to put on the disk), then how to boot it up etc. As for typing commands, it's no different from unix/linux... So go search up about the commands. You should do well, especially if you already got the DOS commands all in your head, it's just learning a few more, even some modifies (some is sim to dos).