Fit the springs to both shoes, then remove, or partly remove, the cam and spindle and place it between the two ends of the brake shoes. You will now have a pair of shoes with a cam and its spindle held together with the spring. Start to insert the spindle back into its hole (that is a good time to ensure there is no corrosion or dirt on the spindle or its containing hole) and then gently slide the four items down towards the brake plate. When it is most of the way in then you will find that the two pivot holes are lined up with the top of their spindles. Move them apart and gently start and slide each shoe down it spindle. Once they have started the whole lot can be slid down towards the plate, the split pins put in and the grease nipple (if your system has one ) for lubricating the cam spindle replaced. Not a spot of blood in sight.