If you get the opto in DIP form (Dual Inline Package – pins in line on both sides of the chip, 2.54mm/0.1" center to center) then it will fit a breadboard and sockets with same spacing holes (not all breadboards are 10 holes per inch but that is standard socket).
I googled quad opto isolator and get many hits, here is one 16 pin 4-channel from the top for 69 cents:
Where it says voltage: 5000V <— that the protection, it takes 5000V to breach the gap. Some optos are good to 10000V or more.
These are for signal current only, about the same as Arduino pins. Best not to feed the input >25mA nor let the output conduct >25mA. Those are 1/2 the maximum which cannot be maintained more than short time. This means that you may need two resistors per channel at most depending on what voltages you are using. If the output connects an Arduino pin set to INPUT mode to 5V (so the pin reads ON when the opto input is HIGH) then no resistor on the output side is needed.
To go from signal level to power level, use the signal to control a transistor and yes, another thing to learn… or find existing circuit or howto.
The datasheet will have the pinout for the chip, it is pretty simple.
I’m not set up for making drawings here nor am I an electronics engineer. WVMARLE knows these things better than I.