Take the lead weight off the plant and separate the individual strands of plant. Then put each stem into the gravel being careful not to damage the bottom of the cutting.
There is no need to trim the cuttings and it's better for the plant if you don't cut it for at least a couple of months. The cutting need time to settle in and develop a root system, then they need to grow. Once they have done that you can take cuttings and trim them up.