MSD 6AL-2 Ignition 2 step rev Control help

Hi I'm hopeing some one can help. i'm not sure what to do with the blue wire for the Two Step Rev Control. do I even need it? the wire from the key to turn on & off the ingnition box can i just use that and twist the blue and red wires together then connect it back to the ingnition (key). I put the istallation guide below. Thanks alot you guy's have been such a big help with everything :)
http://www.msdignition.com/instructions/Products/Ignitions/6421.pdf?terms=6421