The Nexus O has a very simplistic design that was extremely underwhelming when I first took it out of the box. It looks like a giant bull ring -- you know, the kind they show in those old cartoons where the ring goes through the bull's nose.
I took out the instruction booklet, because this was not the same as the prostate massages I've been used to. In the booklet, I noticed that they don't just talk about how to insert the toy, but Nexus also discusses how to breathe, massage, squeeze, and relax while using the toy.
Once it is inserted, the key is to do two things. First, relax. Breathe and relax. Then, rock back and forth on the ground. For a more intense pressure, I recommend sitting on a harder surface. Even a carpeted floor (with a towel laid down) is a hard enough surface to press nicely on the p-spot. On the bed or a pillow is good for those who desire a more gentle rub. Just make sure that whatever you choose, you cover it with a towel. The Nexus O hits my prostate just so, that it makes me pre-cum almost instantaneously.
Once you get used to the feeling, you can use it as long as you want. To practice edging and bring yourself to the ultimate ejaculation orgasm, I suggest rocking on this for a long time. When you get that feeling of needing to cum, start stroking yourself. Right before you hit the point of no return, stop everything. Stop rocking. Stop stroking. Stop thinking about it all. Let your body resorb the energy and, when you're ready again, strat rocking. Continue that process until you just can't take it anymore. You'll know when you reach that point. And then, let it flow.
I can say from experience, years of prostate massage, and paying attention to detail through blogging, the Nexus O is worth every penny of its reasonable ~$50 pricepoint.