Ok for ALL of the people who dont know how to use rar folders this is how.
Go to google and search winRAR and go to or find rarlabs and get the TRIAL version of winrar once downloaded you can extract the files from the rar folder and get the skin file to use the skin. or you can use this link http://www.rarlab.com/download.htm
to get the skin into your osu skins folder(this is how I do it) once you extract the file from the rar find where you extracted it to and find the osu game files and find the skins folder in the game file and drag and drop the skin you extracted into osu's skin folder. Once you have done that open osu and see if that worked.
Also this is important once your winRAR trial is over you do not need to buy it just exit out of the message that pops up when you use it. YOU NEVER NEED TO BUY IT
If this still makes no sense on how to use rars PM me and I will help the best I can