I think there were a couple of iterations of the throttle assembly.. I know that mine has two cables, and the ends slide into the slots on the chain part vertically. Then you make sure the cables are run through the plastic housing correctly, then you set your throttle slack by rotating the grip and setting the gear onto the spool and teeth of the grip. If I remember correctly there may even be a mark on the grip teeth to indicate the correct position.
Finally, you squint one eye, stick out your tongue, and put the cover back on without disturbing anything. Note that if you don't get the cover over the chain slot widget correctly, it won't hold the cables in tightly enough. The cover should sit flush without the screw installed.
Once you do that about three or four times, you'll get it, and it'll be time for a celebratory beverage. (As opposed to a wrenching beverage.)