Two ways as follows:
Stereo as 50/50 watts per side:
The Syn2 Left/Right outputs - into the SYN50/50 A / B ins (far right on the power amp) - then A / B outs (use the left ones first) into 2x50 watt rated cabs.
Mono - 100 watt
The Syn2 Left output - into the SYN50/50 A in (far right on the power amp) - then A out (use the left one first) into a 100 watt rated cab.
NB - if you are running in mono MAKE SURE THE SYN50/50 IS SET TO MONO before you turn it on!