you hold pin through with one finger and hold locking washer in jaws of pliers then press over pin and spring and twist to lock ,you can get a special tool but i still find pliers easier as you can see slot in washer
Put the spring over the stud/locking point place the cup on the end of the spring - hold the rim of the cup with pliers - push the cup against the spring so the slot goes over the locking point - twist the cup 90 degrees