How can I fixwhere the wire connects to the headset?

To fix this problem, you will need a soldering iron and solder(included in this kit), a new TRRS headphone wire(like this one), a spudger or flathead screwdriver, and a Phillips #000 and JIS 1 screwdriver.

Follow this guide to fix the headphones. At step 5, plug in and turn on your soldering iron, then wait for it to heat up(you can test if it's hot enough by trying to melt the solder on the tip).

When the soldering iron is heated up, put the soldering iron on its stand, then hold a wire and solder onto the tip of the soldering iron. Wait until the solder is sucked up into the wire, then move onto the next wire, until all of the wires in the cable are done. Route the wire through the headphones to the speaker.

Remove the blue wire from the speaker by holding a soldering iron on the pad(silver part) and pulling on the blue wire with tweezers. Place the soldering iron back on the pad, then touch solder onto the pad and wait until a small “puddle" forms. Hold the soldering iron and wire on the pad for a few seconds, then remove the soldering iron, keeping the wire held there. Do this for the rest of the wires, one wire at a time.

Make sure the new cable is laying where the old one used to. Reassemble the headphones.