Do you have any images or instructions as to how this piece is put together?
It is fairly straightforward once you get started. Remove the two screws that hold the two chrome halves together. Take the screws out and separate the halves. The throttle tube with the grip will come out of that chrome housing. Unscrew the adjustment screw from the housing. Align the split in the fitting and nut to allow the inner cable with the barrel end to come through to the screw end of that fitting. Screw the fitting and cable into the bottom chrome housing and snug the adjuster down. The barrel end of the cable will fit into a hole in the barrel with the grip. Set the barrel into the bottom of the chrome housing with the barrel in the hole and the inner cable in the slot. Put the top chrome half over the bottom half and reinstall the screws. Keep the screws loose until it is mounted to the bar and tighten them down.