You may be able to do this through Dreamweaver. In the files panel, select 'Remote View' to see the folders and files on your remote (hosted) server, right-click the folder you want to set permissions for, and select 'Set permissions...' from the right-click menu.
Tick the appropriate boxes as per advice in previous posts, and click OK. Check that they have 'stuck' by clicking the refresh icon in the Files panel toolbar, and clicking the set permissions menu item again.