With apache as your web sever this is done via name-based virtual hosts . The client sends the hostname in each request, and that is used by the server to determine which website to use.
Thus if you can configure your dns provider to point multiple dns names at the IP address of your hosting provider, you can then configure your hosting provider to present different websites to different clients, based on which dns name they request. That entails editing your httpd.conf and adding multiple VirtualHost entries. If a process like this is possible with your hosting provider, you can then support multiple different websites.
Note however this can't be done in the httpd.conf, not in a .htaccess file. Thus you have to ask your provider to do it for you.