Rule 1 of the Pendulum - Momentum.
Without momentum, this fighting style means nothing. If you would care to inspect your scythe, or buy one and return, you'll notice the blade if safe heavier than the rest of the weapon. In pendulum style, you use this to your advantage.
First, you must build up momentum. You may stab yourself a lot, so it is better to practise this until you've mastered it with the blade wrapped in leather. To gain momentum, you must swing the weapon around. The faster the weapon goes, the more momentum it has, and the more deadly it is.
If you swing it once then strike, you are losing potential momentum from the weapon. If you give the weapon momentum by swinging it around yourself before striking, the blow can gain more force and thus become more deadly. So, practise swinging the weapon fluidly around you.
Before striking, you must understand that the wild blade can potentially strike you. So, you must control it. Hold the handle lightly, but make sure you are holding it at all times, and do not be afraid to let it slip almost entirely out of your grasp if you are confident you can grasp it again at the last moment to show your mettle and make the audience wow (or strike even more smoothly.)
Once you have mastered swinging the weapon around you, you must learn to do it one-handed. While at most times, especially when striking, it is important you hold the weapon with both hands, otherwise you should be able to control the spinning blade with a single hand so it may go, for example, behind you, above you, and even at times below you. By doing this, you'll also gain the potential to spin it about a set axis, for performance value and to gain momentum with little room, but remember that the weapon is heavy and dropping or losing control can result in disaster. You should only hold it one-handed for brief moments between a firm grasp with both.
Once you believe you have mastered the momentum of the pendulum style in a purely practise or performance area, you are ready to move onto striking.