To do the job properly, you'll need to separate the blades of your pruners. Don't panic, it's just a bolt or a couple of screws. The actual process will vary depending on the make of your pruners, but they are all basically made the same.
Remove the nut or screw holding the two blades together and separate the two pieces. There may be multiple screws on the pruner, but you only need concern yourself now with the one in the center of the two blades. Once the blades are separated, the spring coil between the handles will slip off.