Ok, David just got a good start there for you, thats a great pic of the location of the S12 connectors that you'll need to splice to, he simply cut the connectors off.

^These are stock S12 connectors that you will not use. But for your reference, they are from left to right, A/C compressor clutch connector, Power Steering Pressure Switch connector, and CA20 distributor connector. The thing underneath taped to the harness is a diode block for the tach, just leave it there.

^he did some very interesting things with his wiring, which was very effective but more complex, so I've not explained it to anyone. The green box is the EFI relay, it is normal for it to be on the pass side on MK1 cars, but its usually more hidden. What round thing are you talking about? Those are the battery connections there in your hand...

^This is the plug for the alternator. Excellent pic. Here is what you will need to do: The thick black wire is a supplemental ground for the alternator, so there should be a screw on the
case that it goes to. Now the black 'T' shaped plug is what would normally plug
into the alternator to serve as a field voltage supply (hard to explain atm) but regardless, the KA alternator is set up for an oval plug. Get an oval plug from an S13 or similar nissan alternator and cut the 'T' plug off and splice on the oval plug. On the 'T' plug, is one wire white with a red stripe? (WHITE/RED by my usual naming methods)
There should also be a thick white wire with those connections with an eyelet terminal crimped at the end, that too goes to the alternator, serving as the power output. take a pic of the back of the alternator and I will show you this detail.
As for the starter wire, look for a spade-type connection among these loose connectors in that lower harness. Its usually black and has a rubber sleeve over it. that just pushes onto the spade terminal of the starter. If your car was manual originally, it will be BLACK/YELLOW, and if it was automatic before, it will be BLACK/RED.
These questions are greatly helping my further adjustment of those how-to threads, but for ease's sake, I'll pm you my number, feel free to call and it might be a bit easier to explain, but toss up as many pics and ?s as you like...