I have a dedicated server and a mydomain.com (bought from a hosting company). I want to host a website from my dedicated server with the domain mydomain.com i.e. when I enter mydomain.com from browser it should point to the IP(let's say X.X.X.X) of dedicated server(and a particular folder inside it). I have some following queries:

In Server

1. I know I need to edit some of the files (like: host or hostname file) in the server but I do not know what exact file I need to edit.
2. How to add a Site enable or Site available in apache2 ?

In Hosting Company control Panel

1. Which records to add (A or cname or anyother)?
2. Where Should I add DNS(in dedicated server section or domain name section)?
3. How it is going to affect the behaviour of the domain?

in short the question is: How the virtual host works & how to add DNS?