After registering for my new hosting account I waited overnight to try logging in to cPanel, so that wasn't the issue. Tried again to log in to cPanel after reading djbob's reply...still no luck. Don't know what prompted me to try this, but I decided to enter my username in all lower case, and not the combination upper and lower case that I selected when I initially registered, and that solved the log-in issue. Apparently, cPanel log-in is case-sensitive, and is set up to only accept lower case letters. This was not apparent from reading the welcome email I received after successfully registering, as this letter repeated my username in the same upper and lower case form that I gave during the registration process. For future new users, may I suggest that the welcome letter be changed to alert people to this (or, alternately, adjust the programming of the cPanel log in to accept any combination of upper and lower case).
Djbob, your reply raised another question: you said something about the Apache server needing to restart in 24 hours in order to see my site. Could you please clarify what you mean? Are you talking about the initial subdomain becoming "active", or are you saying that site modifications are not immediately reflected on the "live" site, and take 24 hours to show up?
By the way, my site will use SSI (server side includes) commands, and since they have to be parsed by the server before seeing how they "look" in a browser, I'm assuming that cPanel accomodates this "on the fly" so I can see my site modifications in real time as I'm working on it. Is that a correct assumption?