Let's get started (but please read through these instructions first)

Tools:
Needlenose pliers (or regular pliers)
Soldering iron & solder
12V power source (PC power supply, for example)

First, you'll want to finish your HeatCore. We started it by wrapping the nichrome and applying & curing the first coating of ceramic adhesive. If you ceramic been sitting for a while and seems thick, add a couple of drops of water to thin it.

Locate your Hot-end bag and pull out the bag that contains the HeatCore (the spherical looking thing on a screw with wires sticking out)

Get two of the crimps out of the 'nichrome crimp' bag (look like these) and then cut off the end tabs as shown here.

Then slip the crimp on to one of the nichrome wires with the clasp/tabs end toward the HeatCore. (In Firefox, you can view a larger version of the photo by right clicking and selecting View Image from the menu). The insulation should already have been removed from the exposed wire though there is a probably a little bit remaining near the ceramic.

Leave about a 1/4" (6mm) of nichrome between the crimp and the core. You also want to leave at least a mm of nichrome sticking out of the crimp so that you can fold it over like in the following photo. Once the crimp is in position use your pliers to squeeze the tab/clasp (closest to the core) closed. Then fold the piece of nichrome that is sticking out, back over the crimp.

Attach both crimps as shown here.

Next, attach the male crimps to the Teflon insulated wire. The wire should be pre-stripped. The end with less wire exposed goes into the male crimp as shown below. (In the event that your Teflon wire has not been pre-stripped then strip ~5mm of insulation off one end and ~8mm off the other)

Squeeze one of the tabs over the green insulation.

Then squeeze the other tab over the green insulation.

Then squeeze, one at a time, the tabs onto the exposed wire.

Now add just a touch of solder to secure the crimps to the wire. Do not get solder into other portions of the crimp or you will have trouble getting it into the connector.

Now, insert the Teflon wire into the HeatCore crimp. Leave about 1/2mm of wire exposed - this makes it a little easier to solder it up later.

Here is a helpful NopHead video showing how to crimp without a crimping tool:

Insert the bare end of the green wire into the large female crimp and then squeeze the crimp onto the wire to lock it into position. (Do not insert the male crimp pin into the large female crimp pin.)

Secure the other wire into position.

Now, solder it all like you see here (but do both wires)

Using the included washer, orient your HeatCore leads as shown in preparation for the final ceramic coating. Note the position of the crimps - you don't want the crimps to be above the core (the side where the nichrome comes out off the ceramic) because that side is near the nozzle and it can interfere.

Before you add any ceramic, take at look at the hot-end assembly instructions for your batch and look at how the HeatCore and V3 Hybrid GrooveMount fit together. There is is only ~1mm gap between the HeatCore and GrooveMount - align the crimps as shown here and cover with ceramic as shown. You want to completely cover the crimps and exposed nichrome but not use excessive ceramic. If you add too much ceramic, the Heatcore may bump into the GrooveMount and you'll have to scrape off the excess ceramic to get the heater barrel all the way in. Also, hold your V3 next to your HeatCore - the hook-up wires need enough space to clear the lip of the GrooveMount.

Open the small vial of ceramic and stir it up with the wooden applicator. Cover up ALL exposed nichrome and the crimps. You are applying Cotronics Resbond 907 Fireproof Ceramic Adhesive. Nichrome wire is made to get hot. Apply the ceramic adhesive so that it completely encapsulates the nichrome. Try not to get ceramic on the top or the bottom of the core but if you do you can scrape or sand it off after heating. Ideally you can let this sit overnight but if you don't want to wait you can proceed immediately.

Very Important: At 12 volts and without temperature regulation the HeatCore maximum temperature in open air (uninsulated) is ~360C.  If your HeatCore is mounted with your V3 Hybrid (PEEK) do not heat it without temperature regulation (thermistor or thermocouple) for more than two minutes (at 12 volts). MakerGear hot-ends are not designed to operate at temperatures above 240C. Do not exceed 240C unless you know what you are doing.

You'll need a 12V power source to cure your HeatCore. You can use a PC power supply, an extruder controller, etc. Connect the leads to your power supply (making sure, of course the leads don't touch/short) and turn on the supply. The ceramic will begin to expand, steam and sizzle. How much it steams and expands depends on how long you let it sit. The HeatCore in the following video probably sat for about a day. If you apply heat immediately after applying the ceramic it will expand/steam a lot more.

Let it heat until it starts foaming around the leads and then turn off the power and let it cool for a few minutes. The fresher the ceramic the more times you'll need to repeat this cycle. If it has been sitting over night then doing it 3 or 4 times should do it. Try not to leave the heater on for more than two minutes at a time. You can tell when it is done because most of the HeatCore will be the color it was when you received it.

The last step is too attach the connector. There is a tab inside the connector that fits into the slot on the crimp. Line them up and push it in until it snaps in. You may need a small screwdriver (or something similar) to help you push it in. (The connector in this photo is on backwards d'oh! - the little clasp holds the male and female connectors together and should be away from the heatcore wires)

 Your HeatCore is now ready for action!!