This is still in beta, and i think the server isn't released yet, so just to get that out of the way.
Before we begin, you need Winrar and Java (Google it plox?)
Now on to the client, the download link is:
http://www.mediafire.com/download.php?juwztem21hjnow once you have downloaded the client you will have a lot of files.
go ahead and click 'run.bat' (Or run)
next when this comes up you will see a message about mario being owner. press any key on your keyboard and this box should disappear. Wait a little bit, and the client will pop up.
From there it should be easy.
You should get: