caliper piston retracting tool
This tool has a knife edge on it. Slacken the caliper bleed nipple a little and insert the tool between the brake pad and the disc face. NEVER touch a piston with anything made of metal. Lever the piston back. Withdraw the old pad, making sure that the piston is far enough back to be able to insert a new pad.
Remove and insert 1 pad at a time. The pad locates onto a round pin into the cut out at the bottom of the pad. Make sure that each pad is fitted to the correct depth. Re-locate each spring to secure the pads. Finally, top up any fluid loss and tighten the bleed nipple, then, press the brake pedal a few times to push the pistons out and into their correct position. The pads will need a few miles on them to be efficient on the already worn and groovey disc faces.
The other end dislodges the pad spring from its location on the pad