Clean up Hard Drive and Re-install Mac I have the following MacBook


  MacBook Pro (Retina, 15-inch, Late 2013)


I want to format the hard-disk and reinstall the Mac so that I have a clean system. 
I tried to boot up with CMD + R and reinstall OS. Looks like it didn't wipe out the hard disk and just install the OS again.

Please let me know whats the best way forward. Read a lot of articles are they are confusing. Some say it will get into Internet recovery mode etc.
Boot up holding down Command R, as you did, but go to Disk Utility (under the Utilities menu) and Erase the disk before installing the OS.