MSD 2 Step Rev-Limiter install?Help!

I bought a MSD 2 step rev-limiter from a racing buddy for $30.Problem is no instructions to wire up?I have MSD 6AL box already,how do I hook this up?Car is a stroked 340(372)4 speed with 4.10,s.Any help would be appreaciated.What RPM should I set at for launch?Thanks.