I download flexibility 3 theme at my wordpress blog but when I am going to make some changes I get the following message. I have no idea how to fix this problem? I also do not know where to go to loose the write permissons?

Your stylesheet is not writable. Loosen the write permissions on style.css until you no longer see this message when saving. The default value is 644 on most servers, but you may need to increase it for your particular server. You may also have the theme installed improperly. Make sure the theme folder structure is /wp-content/themes/flexibility3/ and nothing different.

My site url is…www.workwithmarika.com