Like leaning some real skills or having real ability, you have to make a plan first and then finish it.
For me, I have following plans.
First step, you need to learn how to use it. Download it, compile it, test it, and run it (such as a wave function optimization, geometry optimization, CPMD/BOMD for isolated or PBC systems, etc.).
Second step, learn the results of CPMD output, fully understand the meaning.
Third step, learn to change and optimize the CPMD input parameters, and get the meaningful, useful and correct outputs.
Fourth step, learn the code of CPMD, read the related references carefully, if possible, write a module to implement your own program in CPMD, for example, C-DFT in CPMD.
Fifth, if possible, try to combine CPMD and other programs such as GROMACS to run QM/MM simulations.
