Do I need supporting software?

I am an absolute beginner at developing a web site and have uploaded files (photos) to my free ISP provided webspace using SMARTFTP. I know they went because I saw them going on my modem lights and they are also shown in the remote server pane. However, when I try and access the website as a user using the address given by the ISP, I get the message:
'You are not authorised to view this directory page' 'HTTP Error 403 - Forbidden'
Do I need more software? and if so what is it called?