Find the seams at the bottoms of the pockets where you wish to store the speakers, and use a seam ripper to open small holes for the wires to poke through. 

Thread the wires through.

Always leave a little extra wire slack! As you move your body you want the wire to stay loose enough not to pull on any of the components.

Continue installing components and routing wires back to one pocket using your seam ripper. This step is a bit awkward as you have your arms inside the jacket lining trying to route tiny wires.

All your wires should convene in one pocket where you'll store the audio board and battery.

Set up your audio board in a pair of helping hands or panavise, and bring over the wires sticking out of th pocket. Be careful when using your soldering iron near the jacket, accidentally grazing it could leave permanent burn marks.

Solder the speaker wires directly to the outputs marked on the audio board.

Prepare the ribbon wires coming from the triggers by snipping, stripping, and tinning the leads.

Solder these wires to the trigger pins and ground, according to the circuit diagram.