Remove the front plastic casing from the circuit board.

Identify the LED and the foam protector.

Remove the foam protector by gently pulling upwards with thin tweezers.

Use a soldering iron to desolder the LED from the board. Solder the new LED in the same place and orientation.

Never touch a hot soldering iron.

When soldering, be careful not to damage any other components be resting the iron on them. Remove the solder on the LED only, then solder the new one on.