first u must have WinRare program installed on ur computer, u can download the prgram from there
http://www.download.com/WinRAR/3000-2250_4-10007677.html.
How to install the game patch?
1.open the patch fie
2. press on the "extract to" button
3.choose the DreamMu folder , and then press OK and it will be extracted(installed) .