just use a virtual machine (I use virtualbox on my laptop) to try and learn…
I installed NS at least 100 times to setup it in different way, to try something without the fear to destroy anything… and I do the same with other distro too… nowadays we have virtualization tools that help us sooooo much… in the early 2000 years, to make the same test, you have to use real iron… 
you won’t learn much without putting your hands in the mud and enjoying yourself
focus your attention on centos related howtos, get confident with the basilar CLI command… and, using VMs, don’t be afraid to make a mistake 