Thank you for the link, most helpful.
As with most eBay stuff from China, the reality and the description are two different things. What you have there is a not true bistable/latching relay. No, it’s your run of the mill 50 cent 5 volt relay with some mystery four leaded device that does the trigger/hold of the relay. A true bistable relay holds its position without power, the relay you’ve linked to does not and it will always be off upon power up.
The bad news is that this relay will require 60-80ma at all times when the relay is engaged. If you had intended to use this as a zero power latch for battery operation, it’s not going to work.
The good news is that it will most likely not need more than a few milliamperes on the trigger signal pin to get it to change state. You’ll need to source current to the trigger pin so given the original connection diagrams, a low digital output to the opto input led will active the relay rather than a digital high.
Edit: You could always read the coil voltage thru a voltage divider to know the relay state, if that matters to you.