Ypool is windows only :-( But if you're on Linux I guess it should be possible to use the Ypool if you install 'wine' first. This is a software package that let's you emulate a Windows environment (http://www.winehq.org/download/)

Ypool says on their website: "A Linux port of the pool miner is on the way! For the moment we ask Linux users to use wine."

Unfortunately I'm a total n00b. Who knows how to switch to Ypool using 'wine' for Linux using the command line?