You need to put your rear foot tilted a bit

You just really need to practice... You'll get the feel of it soon enough. But what does help putting as little pressure in the nose as possible with it still staying in the 'feeble position' and tilting your back foot.

It's not about leaning back per say, it's about bending your knees properly to distribute your weight over your back truck. Make sure to keep your knees bent when you get on the obstacle you're trying to grind