This article presents how to install Oracle on Centos 6.
Read following article how to install Centos 6 Linux: Install Centos 6 (allocate 64G for disk and set 2G memory for your virtual machine before proceeding with Oracle software installation).
Check latest article How to install Oracle 12C (12.1.0.1) on Centos 6 with UDEV disks, NFS disks, kmod-oracleasm library