But in very vague terms, you will do it exactly like you'd learn to code:
- start reading why/how electricity works[1];
- start making basic circuits with light bulbs or small motors (light bulbs NOT leds) with various switches and try to understand how/why is (not) working;
- start reading to see what basic components are doing: resistors, transistors, diodes, capacitors, transformators/coils; what they do, why they do.
- start combining basic components with the above light bulb. See what happens if you add a resistor or a diode, what a capacitor do and stuff like that.
Jumping from the very begining to arduino boat will only leads to major frustration overtime.
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[1] http://www.instructables.com/id/Electronics-for-Absolute-Beg...
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If you want to also practice, make this as step 1:
- get a soldering iron and some old boards (from an old TV, old radio, stuff that are not build only by integrated circuits) and start exercising (de)sorldering.