1. You can create an account by registering Here. This account can be used then to log into the Game, Website and Forum.

2. Install World of Warcraft Classic Client 1.12.1 (Build 5875). You can download it from the downloads section here: Windows. 

3. In your "World of Warcraft" directory. The default directory is "C:\Program Files\World of Warcraft". Open up the file called "realmlist.wtf" with a text editor such as Notepad. To do this, you must right click on the file and choose properties, then select notepad as the default software for files with the ".wtf" ending. You may also just start the text editor and drag the file into the edit window. 

4. Now erase all text and change it to:

set realmlist enter.razorfen.net

5. You should now be able to log into the client with your new account and start playing.