Problem with WordPress Editing

Hello,

I'm new to the whole WordPress thing. I've already installed WP and have a functional domain address. However, everytime I log into my WP account and try to edit a theme it tells me that I can't save the changes to the theme until I've given the files the right access.

I accessed Dreamhosts WebFTP and tried to look for the WordPress files, but there are none, I only see 2 directories, but nothing about WP, where are the WordPress files located and how can I give them access so that I can edit WP themes.

I need help...I would appreciate it if anyone could give me any tips...

Thank you.

You used the Easy Install, which means you cannot customize it, as the warning for Easy Mode indicates:
WARNING! In easy mode you cannot install your own plugins or themes (though there are a number included). To have full customizability, pick advanced mode below.

-Scott