Identify the soldering terminals inside the earpiece, then secure the wire in place by positioning the exposed end over the correct terminal. There are usually two per side:

One for the signal wire (red or green).

One for the ground wire (bare copper or gold)

With one hand, hold the soldering iron against the wire and terminal for 1–2 seconds to heat the connection.

With your other hand, feed solder to the joint so it melts and flows around the wire.

Remove the soldering iron and let the solder cool for a few seconds before moving the wire.

Repeat for the second wire, ensuring both connections are secure and not touching each other before proceeding.