The SSR4 like other DIY ssrs turns on by grouding the channel feed. You feed it 5v in the pin 1 of the cat5 input you need the "S" jumper near the middle of the pcb jumper for "(S)sr" mode and the C/S jumper jumpered to the "S" side.
Then when you ground pin 2,4,6,8 it turns on channel 1,2,3,4
Hope this helps as far as current you need little so that is not the issue.
RJ