First, install Slackware on a couple text boxen, and one of the BSDs on another.
Network the boxen together (freely available Celeron boxes with built in 10baseT will work nicely for this exercise, or 10base2 "thin net" if you don't have a spare hub). Use the Slackware boxen as "users", and the BSD box as "server". Create several user logins on each box. Along with whatever GUI you use on the main screen, hang a dumb terminal off a serial port on each box, and send it a login prompt. Handy when the GUI goes tits-up.
Then find a copy of the Coherent Lexicon, from Mark Williams Company (try used book stores in University towns). Read it, cover to cover. Yes, including the rather excellent Taylor UUCP tutorial. Try the examples on the Slackware box as a user. Become root, if needed. When you break a Slackware box, learn to repair it in situ, without re-installing the OS.
When you're done with that, get a copy of UNIX Power Tools (O'Reilly). Do the same as the above.
If/when you get stuck, read the man pages; "apropos" and "whatis" can help. Do not ask questions on user forums (Usenet, etc) until you have done a thorough search online ... somebody, somewhere, has already asked & had the exact same problem answered.
Concurrent with this, enroll in "un*x sysadmin 101" (or equivalent) at a local JC/Poly.
Sound old-school? Absofuckinglutely. But you can't run before you can crawl.
 If you don't already know vi & sh inside out, start with those. See "run" and "crawl", above.
 I still use UUCP on internal links for a Usenet system I consult for. I also use it to move email between departments at a couple of Fortune 150s. I'll leave the "why?" as an exercise for the reader.