Eaiest way is with a chain breaker. You can get a good one for about $20. The other way is to grind the head off the pin where you need to break it at and tap it out with a ball peen hammer and a small drift punch. Just be sure you take it apart at the right pin so you have the two outside plates mating up with an inner plate/roller. Also make sure you measure twice before you break it. Your manual or a shop should be able to tell you how many links should be on a chain for your model.