Hi,
You do not need to be a Server Administrator to use mojoPortal. You have not read all of the documentation pertaining to the Multiple Sites feature and you are making assumptions that are taking you down the wrong path.
Considering you're working with the server as a local machine and you don't have a DNS server to setup domains, you can use your localhost file.
There is, in fact, a video on how to do what you are trying to do. You can find that video on the "Host Multiple Sites in a Single Installation of mojoPortal Based on Host Names" article.
Before you watch that video, you should note that since you are running your site in a virtual directory, your final urls will always include the /mojoPortal. There is some very good documentation on how to avoid using a virtual directory on your local machine. That documentation is "Adding a Host Name to the hosts file for local testing." Also be aware that folder-based multiple sites will not work with virtual directories, as noted in this documentation.
HTH,
Joe D.