1. First of all, you must create an account. The account is used to log into both the game, website, and forums. Click here to open the registration page.
2. Install the World of Warcraft 3.3.5a client by choosing one of the following options: Download Torrent.
3. Check your realmlist.wtf file at Data/enUS/realmlist.wtf. Change the contents to:
set realmlist login.oldschool-uberwow.com
4. Now you can simply open Wow.exe and login with the account registered at step 1.
That's it!