Domain/Hosts and MX Records

Before actually continue with my explanation of getting a local web server, here is a live problem I am having:
I have bought a new domain called http://www.scratch-2-win.com, and I want it to start making money for me, so I need people to be able to get to it via the internet, and for this I will need a hosting company.  This means someone that has many computers or very big computers that have a permanent address (kind of like the White House, the preseident will always live there, and such our site will always live at the address we tell it) but how do we tell it where it is living ?
How do I put a domain I have bought on my hosting company ?

So I have a hosting company and now I need to do this, but at the moment I have no idea, luckily I have a friend who is a system admin and he is meant to call me shortly to explain how to do this, and then I can hopefully explain to you how to do this to:

O so I nearly forgot - how do I buy a domain ?  Well this is easy, just type in a Google Search for buying domains and go shopping, personally I bought some from http://www.godaddy.com ok so back to pur problem:

What do you need to do to have your domain pointed towards your web server ?

You need to update the DNS records on the site where you bought your domain from.  Usually you will get a login to wherever you bought a domain from, you will need to login and look how you can edit the DNS records. 
Once you are there you must create what is called "A records" for mail and for the web, so you must add a New Record, for the hostname use mail.hostname.com and use the IP address your hosting company gave you.  Do this for mail, then for www, then for "@"

Hope this has helped, it can take up to 48hours until you start seeing your new website.