|Sorry I didn't respond earlier. I had forgotten about this site.|
Firezilla is indeed a FTP manager. Sorry if these directions aren't spot on specific, but I don't use Firezilla and no longer use Freehostia.
When you signed up for Freehostia, they gave you an account name, login credentials, and a hostname. I think they also specify in that welcome email your FTP credentials which are similar or even the same as your login credentials.
Within Firezilla, there should be a "Connect" section where you'll put in your FTP credentials (host, login, password). I don't think you'll need to enter in the port information.
After Firezilla has you connected, all you do from there is basically drag-and-drop files from your computer to the Freehostia server. After the upload, you should immediately see the changes reflected on your website.