Replace it with an 'E' clip (fit with a pair of pliers), or a snap ring.
If you want to persevere with the 'C' clip, the best way is to fit it in similar way to a piston ring - find something to expand the gap, then force it over the end of the shaft using finger pressure. You wll then be able to slide it down into the groove.
phil_saunders@bigfoot.com
Phil Saunders, December 2008