1) Download the game client .7 on the front page.
2) Extract it somewhere (I use c:\mxo). This is the directory the launcher will ask for at first run.
3) Download the launcher (the .msi) and install it.
4) If running Win 7, right click the mxomu desktop icon and choose 'run as admin' so it saves the directory it asks for.
5) Navigate to where you extraced the game client.
6) Profit.
You of course have to have created a game account and character at the top left of the front page. All of these instructions are on the front page, and questions beyond that are in the FAQ. The FAQ is the first thread in every forum section, and is also in a lot of people's signatures, including my own.
The launcher automatically applies any updates available and connects you to mxoemu's server. It's pretty simple. Read the FAQ before messing around too much, as it details what does and does not work on this obsolete version of the emulator server. This is up for nostalgic purposes while Rajko busts his ass on 'the real deal.'