how do i publish my iWeb to the cloud?

iCloud does not provide hosting services for websites. If you wish to have a website hosted you will need to make arrangements elsewhere. Search Google for various ones or use GoDaddy.com.

As you have iWeb '08, which does not have the FTP facility, you will need to publish your site to a local folder and use an FTP program such as Cyberduck to upload it to a new server.