As for the pin out to turn it on, you will just short PS-ON with the com pin. This should turn the psu on. And I mean one of the little pins, not the large blade even though they are the same thing.
As for putting them together in series, I don't know the dangers of this PSU and I don't know if you will have to break the DC ground on one of them so that you don't get shocked if one goes bad. On the PSU's that I use, you have to disable the DC ground on one of them. Which I did and it works fine.
And as for connecting two in series (for 24 volts) and then two in parallel (for 2000w), again this is going to depend on having to break the DC ground (or should I say isolate it). I have no experience with this PSU so I wouldn't know how to break that ground and render it safe if it shorts out.
