Those instructions are a little bit incomplete. You should open the first page in this thread and read the latest DarkSend Progress Report in .pdf format. Basically you should create a file with the name darkcoin.conf with a line "addnode=23.23.186.131" (without quotes) and put that file in your .darkcoin directory. In that pdf you'll also find a link to the new executable file, download it and replace the one you have now, check permissions, make it executable. Unfortunately, all this has any point ONLY if you have a 64-bit OS.

Hope that helps.