Drew Furgiuele begins his project to build an easy button for backups:
I should also pause for a second and talk about wiring hobby boards like this. Good news first: you won’t electrocute yourself on it. I mean, if you do something really dumb like try to wire it underwater or eat it or something then maybe you could but you shouldn’t ever receive a shock while working with a board like this, even plugged in. The bad news is that even though you won’t damage yourself, you could very well damage the board if you just randomly plug things in. Here’s a hard and fast rule: if you’re not an electronics expert or an electrical engineer, leave it to experts to tell you where and how to wire. I’m not calling myself an expert here, but I have sort of a basic understanding of how to wire these things up. The point I’m attempting at making is: if you want to really learn and understand circuit design, there are lots of great resources of where to get started. And it’s quite a rabbit hole to go down, but it’s well worth your time if you want to learn more.
Read the whole thing. Over a weekend, with your Pi 3.