Put heavy whipping cream in nutribullet with your extractor blade and turn it on and it becomes whipped cream within only a few seconds and you'll know it has become whipped cream because you'll hear it airarate and will not be grabbing the cream anymore.
Now you'll want to put on your milling blade, then turn it on again and pick up the nutribullet and bump it down into the counter a few times until you hear the blade grab the cream again. After it starts to grab it will start to produce some liquid (buttermilk). Which will help it get going but you still might have to bump it into the counter a few more times. Once it grabs good and continues going it only takes a few seconds, so you'll want to keep checking it until it looks like the pic above. Make sure you keep checking it otherwise you could go to far and it will turn back into complete liquid again. If that happens that batch is pretty much junk, so you might want to start with small batches to experiment so you know exactly want is going to happen so you don't waste all your cream..