Okay, two pics and a link.
First pic is yours, with the connectors circled that you need to hook to your I-PAC (or whatever). One goes to ground, the other to the coin input. Doesn't matter which goes where, as long as you use the two that are already connected (if you use the unused one, it'll provide credits constantly EXCEPT when a coin is being inserted - the opposite of what it should do).
Second pic is my coin door, sans wiring, with the actual installed mechanism circled. This is the part you're missing.
This link:
http://www.happcontrols.com/coindoors/42307900.htm is a coin mechanism. These (in general, doesn't have to be this one specifically) are what you need to get to fill in the open areas on your coin door. They'll mount right in there. This is the part that actually determines whether the coin inserted is what the machine is looking for, or needs to be spit back out.
The coin goes in the slot, through the coin mechanism, then if it's accepted it passes through and trips the switch (to which the connectors in the first pic belong) which actually sends the signal to provide the credit.