Please post a photo of a hand drawn schematic diagram showing your complete circuit. You need both a current limiting resistor and a load resistor, something similar to this:
By omitting the required current limiting resistor, the internal LED may have been destroyed.
The basic idea of an optocoupler is that the phototransistor current is approximately proportional to the intensity of the light produced by the internal LED. An optocoupler is not like a relay.
If the LED is destroyed, the optocoupler is useless.
To determine the value of the current limiting resistor, first look up the maximum LED current in the manufacturer's data sheet. Then choose a resistor so that the LED current is less than that. There are tutorials on line.
All I need is current limiting resistor,
You also need a load resistor for the phototransistor.
Thank you for the guidance, still new on the forum, will more details on first post next time
Anyway the led I'm working on is 5v LED, I've tried to directly connect the led to 5v and it works, but when i connect the led driven by optocoupler, it's doesn't turn on
A 5V LED may be 2 LED's in series with a constant current source built in. It will not run if the voltage goes much below 5V.
The opto coupler will have some voltage drop (especially if the led inside is not at max).
Also your opto coupler may not be suitable for power LED's. Do you have any specs on your 5V LED? Or a type nr.?