Couldnt quite get a decent image for where the wire goes into, but thanks anyway
I've never seen this particular lever in person. But I am guessing that the cable mounts on the red cam shaped piece. The cable would normally come in from the hole through the barrell adjuster pretty straight. There's some little metal clip on the red piece (away from the brake lever side), that might be the mounting point. Normally there is a hole with a cup shape that the head of the cable fits in to. You feed the end of the cable without the head through the hole, out the barrell adjuster and keep going until the cable head seats in its spot.
If that doesn't help, try just ratcheting the shifter up and down. The cable has to mount to the piece inside that moves when you do this. Usually in gear 7, the cable will be as far out as it goes and as you shift to gear 1 it will be slowly pulling the cable inside the shifter. So think about where the cable would need to attach for that to happen.
Sorry, can't help more than that.
Yes, do as Dave advised but be sure that you have it in high gear (7th) when installing the cable.
Wheelies don't pop themselves. (from a QBP fortune cookie)