Your Nelson is nearly identical to my Hy-G centrifuge except mine is a bit smaller. If you stare at it for a while then run some cons through it you will pick up how they work pretty quickly. Just keep playing with the settings until you can find no gold in your tails.
The one thing you need to have is lots of water. My Hy-G requires at least 15 GPM and woudl be happier with 20, which is hard to achieve with a garden hose. When you start a run adjust your pressures so you have at lease 8psi positive pressure in the centrifuge bowl. As you feed it the pressure will climb a bit, try to maintain 8-15 psi. If the pressure spikes it is usually because you have let the pressure get too low and you have compacted your values and not the water cant get through...you need to let it work down or you will lose gold.
Like I said...play with it, you will figure it out.
You should also contact Byron Knelson, he loves to talk about his stuff and he has a lot of smart techs.
http://www.knelsongravitysolutions.com/page367.htm