problem with changing themes

Hello, i’ve been using blogger before and it’s my first time using wordpress and it looks great until now !
I have just one problem.
I’ve installed my wordpress blog few minutes ago and now when i’m trying to upload a theme via my admin panel it says this : Unable to create directory /www/clanteam.com/y/o/u/yourtimetofun/htdocs/wp-content/uploads. Is its parent directory writable by the server?

what should i do ? thank you very much !