Using a pair of tweezers grasp the speakers that are located below the battery and pry it off as it is glued onto the phone assembly.

The speakers are connected by a pair of red and blue wires that are soldered onto the SUB PCBA component and will need to be soldered back on.

You can now remove the speakers and replace them.

It might be better to consider replacing the entire SUB-PCBA board instead of just the speakers individually to avoid dealing with the re-connection of the two wires.