By default most theme are set to 644. To edit them online they need to be set at 777.
You can do this via your ftp client or any other method you choose.
To upload your images, you may also need to set your wp-content/uploads folder to 777 as well.
How, using FTP do I change the setting from 644 to 777? I’m using Dreamweaver on a MAC. I don’t understand what I need to do to make the change over.
Thanks