The only difference is Mach number and compressibility. The former is easy - turn the wheel until the "Mach no. index" is in the airspeed window, set the index against the outside air temperature and the Mach number on the inner scale reads against the true airspeed on the outer.
Compressibility is not difficult, but there is a slight complication so that it is probably best taught in the classroom. Wait until your school teaches you.
One piece of advice - if you learnt the "wind-up" method (i.e. marking the wind above the centre of the wheel on the vector calculator) at PPL then teach yourself the "wind-down" method. It should be in the instructions that came with the CRP-5. The CRP-5 is marked for wind-up anyway, that is why it says "True Heading" where all the others say "Index" at the top of the wheel.