It sounds like you will need to update file paths to take into account the new (live) server environment.
If you have Super Administrator access then go to Content->Files->File Upload Preferences and check the paths in there. You will need to specify the paths from the root of your server.
Unfortunately I cannot tell you what should be in there.
If you find that your changes don't 'stick' then it may be that the file upload paths are specified in a config file. To edit this you will need access to the server via FTP. There is also the possibility that the site is using multiple config files with something like Focus Labs Config. In which case it gets a little more complicated as there will be separate files for each environment the site is served in (local, dev, staging, production).
You may also find that you will need to update the permissions on the file upload directories but for that you will need access to the server via FTP, SSH or perhaps your hosting company provides a control panel that will allow you to update the permissions.