Just to sort of get the ball rolling here ..
You need to add the 2 new pucks in series just like the 2 you have now.
Now the "difficulty" is what size power supply do you have.. IF the 24V one you may run out volts and watts
Semi channel is probably the worst..
V(f) could be about 4 volts..that's 8 volts per board x 4 boards = 32V needed...
48V power supply will be fine..
Which do you have?
Other config would be 2 in series 2 in parallel but not really a good idea..
I see the duo should come w/ the 48V power supply, meaning you have about 45V to play with.
Plus out from driver board (driver side) to plus on puck 1
minus on puck 1 to plus on puck 2
(what you should have now, only minus will go to driver board from puck 2)
minus on puck 2 to plus puck 3
minus on puck 3 to plus on puck 4
minus on puck 4 to driver board negative (driver side)..
Each channel is the same
I'll let others verify...
noticed that you state you haven't soldered before.. that could be an issue...
It's not hard but "rookies" (and others, no judgement here) run the risk of over-heating the contact pads and screwing up the trace...or a cold solder joint that eventually lets go.
Or too much solder bridging the contact points..