For sustained spinning with your hoop, you're going to put yourself in one spot, so find a spot on the ground that's nice and level because you're going to be turning in that same spot for a while.
What you want to do with your hoop is you want to try to keep the hoop level, horizontal at all times. The idea behind sustained spinning is that your body is the center point of the hoop, and the hoop is floating around your body staying level.
Probably the hardest part about sustained spinning is not getting dizzy. What you can do to help with that is focus on one spot in front of you as your rotate keeping the hoop horizontal, focusing on that spot, and turning your head quickly and seeing that spot once again. That will help to keep you from getting dizzy. I'd practice that slowly first, turning your body, keeping the hoop nice and level.
Turn your head, similar to spotting if you've ever taken dance classes. Then, you can go the other way. Notice how the hoop stays nice and level. Now, the way to make this look really cool is to move the hoop up and down your body as you are turning. So starting, rotating, making sure you find your spot, bringing the hoop up, and back down. Notice that my feet are taking little steps around in a circle, nice and smooth.
Let's go the other way. Make sure you unwind after staying in one direction after a while. Once you're starting to feel comfortable with that, bringing the hoop up and down from your hips to up above your head, you can then start to bend down and bring it all the way to the floor.
So we can practice this motion first. We'll start with it overhead, keeping it level. Notice how my hands are inside the hoop, my elbows pulled down. Then I'm rotating now. My hands are outside the hoop, and I'm bending down keeping it nice and level all the way up.
So now, we try that with our sustained spinning. Rotate to the left, bring it down, keep it level, make sure you find your spot. Reverse the other way. That's how you do sustained spinning.