Things you will need:
A small possie head/Philips screw driver
A small flat head screw driver (possibly)
Remove the screw at the side of the valve and pull away the contact block.
The terminals are inside the block just removed.
Pry out the inner part with the flat head screw driver.
Top left is positive/VCC and top right is negative/GND
The bottom terminal is AC EARTH and not used when using DC.
Feed the end of the wire through the outer shell.
Attach the wires to the terminals. Red to the left, black to the right. Position the wires so they will not interfere with the screw.
Make sure the actual metal part of the wire is making contact with the terminal.
Push the terminal block back in to the outer shell. You may need to pull the wire through at the same time.
Puch the terminal block on to the main valve and put the screw back in.