Most push and self propel lawn mowers have the pull cord assembly attached to the top of the mower by 3-4 small bolts. Remove the bolts and the pull cord unit should lift right off. Go ahead and remove the cord. When doing this, the spring will most likely unwind. Before you put the new pull cord in, make sure to rewind the spring and either clamp it or use a screwdriver to hold it while you get the rope. Once you get it, let the spring loosen the wheel .5 to 1 turn then install the rope. It should retract the rest of the way in and now you simply just install the unit back to the mower!