trying to understand on DNS Setup

Ok, I have tried on looking up on setting up DNS with namecheap the proper way and there isn’t one, I like to know how to setup the domain and nameserver is detail as possible, I mean detail in laming terms and the update tutorial from the old version virtual to the newest version of virtualmin that we have now. Because i tried to setup the DNS and it just doesnt work, i wait for propergation in the 48 to 72 hrs and the DNS just doesn’t work. Namecheap there Nameservers i set them up pointing to the ip addresses , so i would like a detail tutorial on namecheap setup nameserver to virtualmin, and domain setup, I know its probably not a place for namecheap tutorial but come on somebody has to know the setup easily. oh yes I use Ovh VPS and Dedicated Server, I am perm disabled and they are cheap and within my budget. So anyways that’s my 2 cents. So pretty please provide a really good tutorial on setup the DNS.