upon turning over the panel you can see which parts the LEDs are soldered on to (highlighted in the pic below). take your soldering iron and remove the LEDs by melting the metal. i found that this was a bit difficult to do so i broke off the LEDs. once the LEDs have been removed you are ready to begin fixing on the new ones.
i have taken my LEDs from 2 old
PSU fans (be careful when opening up PSUs, do so at risk). the LEDs were attatched to some wire but they were easily unsoldered.