I use the Astron with the FX preamp but I'm not sure it sounds any better than the much cheaper Pyramid. I use the 19v power brick that allo sells and recommends for the Volt+D. The whole point of the CM's ( that are built into the +D ) is so you can use a cheaper power supply.
These male plugs should fit the FX female input and they are marked + and -. You loosen the screws on top insert the hook up wires in the holes and tighten them down.
https://www.amazon.com/gp/product/B015OCV5XO/ref=ox_sc_act_title_1?smid=A26VCHUIBE4PN9&psc=1
Hook up wires should be stranded and no larger than 18 gauge. 20 gauge is probably ideal. You can use speaker wire or just buy a roll of hook up wire from Home Depot or Lowes.
The linear regulated psu has a red + terminal and a black - terminal and observing polarity the hook up wire is connected to these terminals.