Hi Mick.
Okay, so if you look at the diagram, the upper right terminal of the CDI is the output to the coil. Of course you must obtain a suitable coil. There are thousands of them out there; just look for something you would use on a scooter. So, if you are to run twin spark plugs, you will need to purchase two coils. You will also have to obtain a small 12 volt battery. The upper right output terminal of the CDI can power both coils. One wire of the coil is to be grounded, and I think it is usually a green wire, the other wire goes to the upper right terminal of the CDI. Since you will run two coils, both those wires (one from each coil) will connect together to that output terminal of the CDI. I just ordered a wiring harness for the GY6 scooter, and it should have the right kind of plugs to fit the CDI. You could do the same too, if you want to build a nice harness. Unfortunately, the wiring harness costs about 45 dollars, and all I'm going to use is two plugs! What I did the first time running the DC fired CDI was to solder the wires directly to the CDI terminals. It didn't look like a factory job, but it worked totally fine. I am slowly, but steadily working on developing a nice twin ignition kit, but it will take some time, and they will be a little pricey. I will post some pictures soon of the work I'm doing with this. I'm developing some aluminum pieces that will actually fit to the gas tank studs used for mounting the gas tank. The battery pack/s and the cdi will fit underneath the gas tank. There will also be two aluminum side panels to hide those components. The side panels can also be used for mounting a charging plug and a on/off switch. The battery packs and the cdi take up most of the room underneath the gas tank, so I thought the coils could be mounted on the outside surface of these panels. I have a lot of work, so it might be a couple of weeks before I can put those images up here for you to see.
Keep up the good work; this is all really new stuff, I think I may only be one step ahead of you on this, so whatever help you or anyone else is willing to contribute would be very good.
Thanks
-Fred