Can’t upload images, permissions problem

Hi, and thanks in advance.

I’ve created a WordPress site for someone on a server/host they already have a plan with (and they want to stay on that host). WordPress more or less installed without a hitch, but when I go to upload images I get this error:

Unable to create directory /home/websitename/public_html/wp-content/uploads/2010/05. Is its parent directory writable by the server?

When I log in to cPanel and go to File Manager to try to edit permissions, the permissions button is gray-ed out/inactivated. Is there some other permissions menu I need to be at?

Thanks again,
Christian