Hi Julie,
Simply use a pair of wires (22 gauge is fine) connected to the 12 volt out on the s SP2 -use the "C" and "on/OFF".
Connect those two wires to the two 12 volt 'inputs' on the first amplifier and then the 'outs' on that amplifier to the 'ins' on the second amplifier.
Set the amplifier switch on the back to Remote trigger - 'REM' or 'External' depending on the amp and you should be set.
james