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What is the problem you have?
You can connect the optocoupler diode directly (with a resistor of course ) if your mcu can provide the current that you need for the diode, if not you have to use a transistor to provide more current.
A higher current in the diode will give a higher current in the optocoupler transistor.
The optocoupler doesn't have a power supply, it has a diode in the input that can work will a voltage of 2v (Check Vf in the datasheet) or more and the output is a transistor that can be connected to any voltage and configuration assuming that you don't exceed the transistor max ratings (voltage, current, power)
You can use any standard opto-coupler. The input side of the opto-coupler is a LED. If you just limit the current flowing through to the LED, then you have no problem using it at 5v or (much) higher. The output side is the transistor. The maximum voltage that can be applied/connected to the transistor depends on which opto-coupler you are using. So, it's best to check the datasheet for that. You can find the datasheet from a site such as Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view . A few common opto-couples are 4N25, 4N35, MCT2E, PC817, TLP521, etc