I was pretty much self taught just by watching how others did it and them allowing me to do it as well as showing me, took some time and a few mistakes but I got there in the end.
I took a hands-on computer class in high school, but I knew a little bit before that. Once you've taken it apart, you really don't have any choice but to put it back together correctly, hahaha. 😛
I had a friend help me build mine. He actually sort of built 75% of it while I got him some food and drinks. I wasn't expecting him to be so quick, lol.
I learnt when I was involved in electronic engineering in commercial radio broadcasting, from the old days when DOS was virtually the main operating system up until now.