No it wants to download the rest of the installer to finish the job. It wants any internet connection, preferably on the machine your trying to install Firefox on.

So next time have a connection go here and download the full installer and it can then be installed off line. https://www.mozilla.org/en-US/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Creating a Firefox Account and using the Sync service is completely optional. If it holds no interest for you, just ignore that and browse as you wish. You can click the house button on the toolbar or press Alt+Home to get to the Firefox home page (or whatever home page you prefer, see: How to set the home page).